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ΑΡΙΘΜΟΙ 3001 - 4000

3001 is 1/24 of the 24^th Fibonacci number.

3003 is the only number known to appear 8 times in Pascal's triangle.

3005 is the number of functions from {1,2,3,4,5} to itself that are not injections.

3006 has a square with the last 3 digits the same as the 3 digits before that.

3008 is the number of symmetric plane partitions of 29.

3010 is the number of partitions of 27.

3012 is the sum of its proper divisors that contain the digit 5.

3015 is a value of n for which n, 2n, 3n, and 4n all use the same number of digits in Roman numerals.

3016 is a value of n for which n φ(n) is a palindrome.

3020 is the closest integer to π⁷.

3024 = ₉P₄.

3025 is the sum of the first 10 cubes.

3026 is the number of 10-ominoes that tile the plane isohedrally.

3028 are the first 4 digits of 5³⁰²⁸.

3031 is the number of 7-kings.

3032 is the number of trees on 19 vertices with diameter 5.

3036 is the sum of its proper divisors that contain the digit 5.

3038 has a square that remains square when a 9 is appended to it.

3044 is the number of nonisomorphic unlabeled binary relations on 4 elements.

3045 = 196 + 197 + . . . + 210 = 211 + 212 + . . . + 224.

3049 is the number of ways to tile a 8×4 rectangle with integer-sided squares.

3053 in hexadecimal spells the word BED.

3054 = 6 × 7 × 8 × 9 + 6 + 7 + 8 + 9.

3055 is a number with the property that the root-mean-square of its divisors is an integer.

3056 is a structured snub dodecahedral number.

3057 is the number of rooted ternary trees with 12 vertices.

3058 is the number of 7-digit triangular numbers.

3059 is a centered cube number.

3060 = ₁₈C₄.

3063 is a perfect totient number.

3066 is the average of the first 853 primes.

3068 is the number of 10-ominoes that tile the plane.

3069 is a Kaprekar constant in base 2.

3070 is the number of paraffins with 9 carbon atoms.

3072 is the smallest number with exactly 22 divisors.

3074 is the number of binary partitions of 37.

3077 is the rectilinear crossing number of complete graph K₂₃

3078 is a pentagonal pyramidal number.

3080 is the number of drawings of the complete graph K₉ with a minimal number of Achilles number.

3089 is the smallest prime so that it and the next 2 primes all end in 9.

3092 is a structured truncated tetrahedral number.

3094 = 21658 / 7, and each digit is contained in the equation exactly once.

3096 is the number of 3×3×3 sliding puzzle positions that require exactly 7 moves to solve.

3097 is the largest known number n with the property that in every base, there exists a number that is n times the sum of its digits.

3101 is the number of ways to color the vertices of a triangle with 21 colors, up to rotation.

3103 = ₂₂C₃ + ₂₂C₁ + ₂₂C₀ + ₂₂C₃.

3105 is a member of the Fibonacci-type sequence starting with 2 and 7.

3106 is both the sum of the digits of the 16^th and the 17^th Mersenne prime.

3107 is the number of ways to divide a 10×10 grid of points into two sets using a straight line.

3109 is the smallest prime n so that n/π(n) > 7.

3110 = 22222 in base 6.

3112 is the number of 10-digit strings where consecutive digits differ by exactly 1.

3114 has a square containing only 2 digits.

3115 has the property that if each digit is replaced by its square, the resulting number is a cube.

3119 is a right-truncatable prime.

3120 is the product of the first 6 Fibonacci numbers.

3121 = 3121₅ + 3121₇ + 3121₈.

3122 is the number of ordered sequences of coins totaling 29 cents.

3124 = 44444 in base 5.

3125 is a strong Friedman number.

3126 is a Sierpinski Number of the First Kind.

3127 is the product of two consecutive primes.

3135 is the smallest order of a cyclotomic polynomial whose factorization contains 7 as a coefficient.

3136 is a square that remains square if all its digits are decremented.

3137 is the number of planar partitions of 17.

3139 is the 9^th central trinomial coefficient.

3141 is the integer part of 1000 π.

3146 is a structured deltoidal hexacontahedral number.

3148 is the number of different degree sequences possible for a graph with 9 vertices.

3150 is a value of n for which n, 2n, 3n, and 4n all use the same number of digits in Roman numerals.

3153 = 1¹ + 3³ + 5⁵.

3156 is the sum of its proper divisors that contain the digit 5.

3159 is the number of trees with 14 vertices.

3160 is the largest known value of n for which _2nC_n is not divisible by the first 5 primes.

3161 is the smallest number whose square begins with three 9's.

3162 is the largest number whose square has 6 digits.

3163 is the smallest number whose square has 7 digits.

3168 has a square whose reverse is also a square.

3169 is a Cuban prime.

3171 is the sum of the squares of 3 consecutive primes.

3173 is the number of different degree sequences possible for a graph with 16 edges.

3174 is the first of four consecutive squareful numbers.

3178 = 4321 in base 9.

3179 is the number of 13-ominoes that tile the plane by translation.

3180 has a base 3 representation that ends with its base 5 representation.

3181 has a base 3 representation that ends with its base 5 representation.

3182 has a base 3 representation that ends with its base 5 representation.

3184 is a value of n for which |cos(n)| is smaller than any previous integer.

3185 is the number of ways to legally add 2 sets of parentheses to a product of 13 variables.

3186 is a value of n for which _2nC_n is not divisible by 3, 5, or 7.

3187 is the smallest value of n for which n and 8n together use each digit 1-9 exactly once.

3189 is the number of non-commutative non-associative closed binary operations.

3190 is a narcissistic number in base 7.

3191 is the smallest number whose reciprocal has period 29.

3192 is the number of planar graphs with 8 vertices, all with degree 2 or more.

3195 is the number of congruency classes of triangles with vertices from a 12×12 grid of points.

3200 is the number of graceful permutations of length 13.

3203 has the property that if each digit is replaced by its square, the resulting number is a square.

3206 is the smallest number whose square contains 8 different digits.

3210 is the smallest 4-digit number with decreasing digits.

3212 = 3⁷ + 2⁹ + 1⁷ + 2⁹.

3214 is the maximum number of regions a circle can be cut into by joining 17 points on the circumference with straight lines.

3216 is the smallest number with the property that its first 6 multiples contain the digit 6.

3217 is the exponent of a Mersenne prime.

3218 has the property that the concatenation of its prime factors in increasing order is a square.

3225 is the number of symmetric 3×3 matrices in base 5 with determinant 0.

3226 is the number of 12-iamonds without holes.

3229 is a value of n for which one more than the product of the first n primes is prime.

3232 is the number of isomers of C₁₂H₂₄ without any double bonds.

3237 is the number of groupoids on 3 elements with no symmetry.

3240 is the number of 3×3×3 Rubik's cube positions that require exactly 3 moves to solve.

3242 has a square with the first 3 digits the same as the next 3 digits.

3243 in hexadecimal spells the word CAB.

3244 is the number of asymmetric trees with 18 vertices.

3245 in hexadecimal spells the word CAD.

3247 is the number of connected graphs with 9 vertices and 25 edges.

3248 is the number of legal bishop moves in Chess.

3249 is the smallest square that is comprised of two squares that overlap in one digit.

3250 is a value of n for which _2nC_n is not divisible by 3, 5, or 7.

3251 is a number n for which n, n+2, n+6, and n+8 are all prime.

3252 is the number of graphs with 9 vertices and 11 edges.

3254 = 33 + 2222 + 555 + 444.

3255 is a value of n for which φ(n) = φ(n+1).

3259 = 33 + 2222 + 5 + 999.

3262 is the number of graphs with 9 vertices that have 6 automorphisms.

3264 is the number of partitions of 49 into distinct parts.

3265 is the smallest n for which 34n contains only 0's and 1's.

3267 = 12345 in base 7.

3274 = 303022₄ = 101044₅, each using 3 different digits exactly twice.

3276 = ₂₈C₃.

3277 is a Poulet number.

3280 = 11111111 in base 3.

3281 is the sum of consecutive squares in 2 ways.

3282 is the sum of its proper divisors that contain the digit 4.

3283 is the number of 3×3 sliding puzzle positions that require exactly 15 moves to solve starting with the hole on a side.

3285 is the magic constant for a 9×9×9 magic cube.

3286 is the number of stable patterns with 16 cells in Conway's game of Life.

3290 is an enneagonal pyramidal number.

3292 is the number of ways to tile a 4×27 rectangle with 4×1 rectangles.

3294 is a value of n for which 6n and 7n together use each digit exactly once.

3295 is the number of self-dual binary codes of length 32.

3296 is the number of lines passing through at least 2 points of an 11×11 grid of points.

3297 is a value of n for which 5n and 7n together use each digit exactly once.

3298 is the number of trees with 7 vertices.

3300 is the number of groupoids on 4 elements.

3301 is a value of n for which the n^th Fibonacci number begins with the digits in n.

3302 is the maximum number of pieces a torus can be cut into with 26 cuts.

3303 is a centered octahedral number.

3304 is the maximum number of regions a cube can be cut into with 27 cuts.

3305 is the number of rectangles with corners on an 10×10 grid of points.

3306 is the number of non-associative closed binary operations on a set with 3 elements.

3309 is the number of ways to break {1,2,3, . . . ,16} into sets with equal sums.

3311 is the sum of the first 21 squares.

3312 = 33² + 12².

3313 is the smallest prime number where every digit d occurs d times.

3318 has exactly the same digits in 3 different bases.

3320 has a base 4 representation that ends with 3320.

3321 has a base 4 representation that ends with 3321.

3322 has a base 4 representation that ends with 3322.

3323 has a base 4 representation that ends with 3323.

3324 is the maximum value of n so that there exist 4 denominations of stamps so that every postage from 1 to n can be paid for with at most 20 stamps.

3325 is the smallest number that can not be written as the sum of 3 volumes of rectangular boxes with integer dimensions less than 13.

3326 is the smallest integer ratio of a 17-digit number to its product of digits.

3329 is a Padovan number.

3330 is a value of n for which n-1 and n+1 are twin primes, and so are 2n-1 and 2n+1.

3331 is the number of monoids of order 7 with 3 idempotents.

3333 is a repdigit.

3334 is the number of 12-iamonds.

3335 is the smallest number whose square contains 4 consecutive 2's.

3337 has a cube with only odd digits.

3338 is a member of the Fibonacci-type sequence starting with 3 and 7.

3339 is a value of n for which σ(n) = 3φ(n).

3340 = 3333 + 3 + 4 + 0.

3341 = 3333 + 3 + 4 + 1.

3342 = 3333 + 3 + 4 + 2.

3343 = 3333 + 3 + 4 + 3.

3344 = 3333 + 3 + 4 + 4.

3345 = 3333 + 3 + 4 + 5.

3346 = 3333 + 3 + 4 + 6.

3347 = 3333 + 3 + 4 + 7.

3348 = 3333 + 3 + 4 + 8.

3349 = 3333 + 3 + 4 + 9.

3358 is the sum of the squares. of the first 11 primes.

3360 = ₁₆P₃.

3361 is the number of quasi-triominoes that fit inside a 12×12 grid.

3362 has a square whose digits each occur twice.

3363 is a number n for which n²+1 is double another square.

3366 = (1⁹ + 2⁹ + 3⁹) / (1 × 2 × 3).

3367 is the smallest number which can be written as the difference of 2 cubes in 3 ways.

3368 is the number of ways that 5 non-attacking bishops can be placed on a 5×5 chessboard.

3369 is a Kaprekar constant in base 4.

3375 is a Friedman number.

3376 is the number of digits of the 23^rd Mersenne prime.

3378 is a Friedman number.

3379 is a number whose square and cube use different digits.

3380 would be prime if preceded and followed by a 1, 3, 7, or 9.

3381 is the number of ways to 14-color the faces of a tetrahedron.

3382 is a value of n for which 2φ(n) = φ(n+1).

3383 has the property that the sum of its prime factors is equal to the product of its digits.

3386 has a square whose digits each occur twice.

3390 is a value of n for which n-1 and n+1 are twin primes, and so are 2n-1 and 2n+1.

3400 is a truncated tetrahedral number.

3402 can be written as the sum of 2, 3, 4, or 5 positive cubes.

3403 is a triangular number that is the product of two primes.

3404 is the number of binary partitions of 38.

3405 is a structured great rhombicosidodecahedral number.

3408 = 3³ + 4⁴ + 5⁵.

3410 is a truncated square pyramid number.

3411 is the number of inequivalent asymmetric Ferrers graphs with 31 points.

3412 = 2² + 3³ + 4⁴ + 5⁵.

3413 = 1¹ + 2² + 3³ + 4⁴ + 5⁵.

3417 is a hexagonal pyramidal number.

3420 is the order of a non-cyclic simple group.

3427 is a member of the Fibonacci-type sequence starting with 1 and 5.

3431 is the number of inequivalent Ferrers graphs with 31 points.

3432 is the 7^th central binomial coefficient.

3433 is a narcissistic number in base 6.

3435 = 3³ + 4⁴ + 3³ + 5⁵.

3439 is a rhombic dodecahedral number.

3440 is the closest integer to 20^e.

3444 is a stella octangula number.

3447 is the smallest value of n for which 2n and 5n together use the digits 1-9 exactly once.

3451 is the number of conjugacy classes of the alternating group A₃₁.

3456 has digits in arithmetic sequence.

3457 is a Proth prime.

3459 has a 6^th root that starts 3.88888....

3461 is a number n for which n, n+2, n+6, and n+8 are all prime.

3462 is the number of integer solutions to 1 = 1/x₁ + 1/x₂ + 1/x₃ + 1/x₄ + 1/x₅ + 1/x₆ for 1≤x₁≤x₂≤x₃≤x₄≤x₅≤x₆.

3465 = 15!!!!.

3468 = 68² - 34².

3476 is a value of n for which n!! - 1 is prime.

3478 has the property that dropping its first and last digits gives its largest prime factor.

3480 is a Perrin number.

3482 is the smallest number n so that n² is 1 more than 43 times a square.

3485 is the maximum value of n so that there exist 8 denominations of stamps so that every postage from 1 to n can be paid for with at most 8 stamps.

3486 has a square that is formed by 3 squares that overlap by 1 digit.

3487 is the number of squares in a 14×14 grid of squares with diagonals drawn.

3488 has a 5^th root that starts 5.11111....

3489 is the smallest number whose square has the first 3 digits the same as the last 3 digits.

3492 is the number of labeled semigroups of order 4.

3498 is a number whose sum of divisors is a 5^th power.

3499 in hexadecimal spells the word DAB.

3501 is a value of n for which n, 2n, 3n, and 4n all use the same number of digits in Roman numerals.

3502 is the number of 3×3×3 Rubik's cube positions that can result from 3 quarter or half turns.

3507 is a value of n for which n! - 1 is prime.

3510 = 6666 in base 8.

3511 is the largest known Wieferich prime.

3521 = 3333 + 55 + 22 + 111.

3522 is the sum of its proper divisors that contain the digit 7.

3525 is a Pentanacci number.

3527 is the number of ways to fold a strip of 10 stamps.

3528 is an Achilles number.

3531 is a value of n for which φ(n) = φ(n-2) - φ(n-1).

3534 is the number of 5-step self-avoiding walks on the cubic lattice.

3536 is a heptagonal pyramidal number.

3539 is a value of n for which |cos(n)| is smaller than any previous integer.

3541 is the smallest number whose reciprocal has period 20.

3542 is the number of ways to write 16 as an ordered sum of positive integers, where adjacent numbers are different.

3543 has a cube containing only 3 different digits.

3552 is a value of n for which n φ(n) is a palindrome.

3554 + σ(3554) = 8888.

3563 is a house number.

3564 divides 1¹ + 2² + 3³ + ^{. . .} + 3564³⁵⁶⁴.

3570 is both a triangular number and 6 times a triangular number.

3571 is the 17^th Lucas number.

3575 is the smallest n for which 28n contains only 0's and 1's.

3577 is a Kaprekar constant in base 2.

3579 has digits in arithmetic sequence.

3581 is the smallest n for which 31n contains only 0's and 1's.

3583 is the smallest number requiring an addition chain of length 16.

3584 is not the sum of 4 non-zero squares.

3585 has a 10^th power that contains the same digits as 9036⁹.

3588 is the maximum number of regions space can be divided into by 23 spheres.

3593 is a prime that is the average of two 4^th powers.

3594 is the smallest number whose 9^th power has 32 digits.

3596 is the number permutations of {1,2,3,...,19} where adjacent numbers differ by no more than 2.

3599 is the product of twin primes.

3600 is the order of a perfect group.

3605 is a centered tetrahedral number.

3607 is a prime factor of 123456789.

3609 is the number of multigraphs with 22 vertices and 4 edges.

3610 is a value of n for which n! - 1 is prime.

3612 is a narcissistic number in base 7.

3613 is a narcissistic number in base 7.

3616 = 1111 in base 15.

3620 is the trinomial coefficient T(16,12).

3622 is the number of ways of placing 26 points on a 13×13 grid so that no 3 points are on a line.

3623 times the 3623^th prime is a palindrome.

3624 is the first of five consecutive squareful numbers.

3626 is a member of the Fibonacci-type sequence starting with 1 and 9.

3628 is the number of ways to place 3 non-attacking queens on a 7×7 chessboard.

3630 appears inside its 4^th power.

3632 is a value of n for which n φ(n) is a palindrome.

3635 has a square with the first 3 digits the same as the next 3 digits.

3638 is the number of ways to stack 26 pennies in contiguous rows so that each penny lies on the table or on two pennies.

3640 = 13!!!.

3641 is an hexagonal prism number.

3645 is the maximum determinant of a binary 12×12 matrix.

3648 is the number of subsets of {1,2,3,...,15} that have a sum divisible by 9.

3650 is the number of binary cube-free words of length 19.

3652 is the number of fixed 7-hexes.

3654 = ₂₉C₃.

3655 is the sum of consecutive squares in 2 ways.

3657 is a structured truncated octahedral number.

3658 is the number of forests with 13 vertices.

3660 is the number of connected graphs with 6 vertices and 6 edges.

3663 is a palindrome in base 8 and in base 10.

3664 is the number of graphs with 10 vertices and 9 edges.

3665 would be prime if preceded and followed by a 1, 3, 7, or 9.

3671 is the number of 9-abolos.

3673 is the number of ways a 8×1 rectangle can be surrounded by 8×1 rectangles.

3678 has a square comprised of the digits 1-8.

3679 is the number of ways to stack 17 pennies in a line so that each penny lies on the table or on two pennies.

3681 is the maximum number of pieces a torus can be cut into with 27 cuts.

3683 is the maximum number of regions a cube can be cut into with 28 cuts.

3684 is a Keith number.

3685 is a strong Friedman number.

3686 would be prime if preceded and followed by a 1, 3, 7, or 9.

3690 is the number of trees on 29 vertices with diameter 4.

3691 is a number n for which n²+1 is triple another square.

3696 is the number of ways to color the vertices of a square with 11 colors, up to rotation.

3697 is the smallest number in base 6 whose square contains the same digits in the same proportion.

3698 has a square comprised of the digits 0-7.

3699 is the rectilinear crossing number of complete graph K₂₄

3700 is the sum of the squares of 4 consecutive primes.

3702 = 3 + 33 + 333 + 3333.

3703 is the smallest number that can not be formed using the digit 1 at most 26 times, together with the symbols +, –, × and ÷.

3705 is the generalized Catalan number C(16,4).

3709 is a value of n for which 2n and 7n together use the digits 1-9 exactly once.

3710 is a number whose sum of divisors is a 5^th power.

3711 is the number of multigraphs with 6 vertices and 10 edges.

3714 is the number of graphs with 8 vertices and edge-connectivity 1.

3715 is a member of the Fibonacci-type sequence starting with 3 and 8.

3718 is the number of partitions of 28.

3720 = 225 + 226 + . . . + 240 = 241 + 242 + . . . + 255.

3721 is the number of partitions of 46 in which no part occurs only once.

3723 has a 4^th power that is the sum of four 4^th powers.

3728 is the smallest number whose 7^th power has 25 digits.

3729 is a value of n for which n and 5n together use each digit 1-9 exactly once.

3731 is a dodecagonal pyramidal number.

3733 is a right-truncatable prime.

3734 is the number of binary partitions of 39.

3739 is a right-truncatable prime.

3740 is the sum of consecutive squares in 2 ways.

3743 is the number of polyaboloes with 9 half squares.

3745 has a square with the last 3 digits the same as the 3 digits before that.

3747 is the smallest number whose 9^th power contains exactly the same digits as another 9^th power.

3750 is the first of four consecutive squareful numbers.

3751 has the same digits as the 3751^st prime.

3752 is a cubic star number.

3753 has a cube that is the sum of 3 positive cubes.

3760 is a substring of any power of itself.

3761 is the first year of the modern Hebrew calendar.

3762 is the number of bicentered trees with 15 vertices.

3763 is the largest n so that Q(√n) has class number 6.

3765 is the number of series-reduced planted trees with 18 vertices.

3767 is the smallest number with complexity 28.

3771 is a value of n for which 4n and 7n together use each digit exactly once.

3773 is a structured great rhombicubeoctahedral number.

3777 is a Pentanacci-like number starting from 1, 1, 1, 1, and 1.

3780 is a highly abundant number.

3784 has a factorization using the same digits as itself.

3786 = 3⁴ + 7⁴ + 8 + 6⁴.

3788 is the number of 9-hexes that tile the plane.

3789 divides the sum of the digits of 3789!.

3791 is the number of symmetric plane partitions of 30.

3792 occurs in the middle of its square.

3793 is a right-truncatable prime.

3795 is the sum of the first 22 squares.

3797 is a right-truncatable prime.

3798 is a value of n for which 2n and 9n together use the digits 1-9 exactly once.

3802 is the nearest integer to (5 + 1/5)⁵.

3803 is the largest prime factor of 123456789.

3804 is a member of the Fibonacci-type sequence starting with 2 and 5.

3807 and its successor are both divisible by 4^th powers.

3808 is the generalized Catalan number C(12,5).

3810 is the number of ways to place a non-attacking white and black pawn on a 9×9 chessboard.

3811 is the number of polycubes containing 8 cubes, if mirror images are not counted as different.

3812 is the maximum value of n so that there exist 4 denominations of stamps so that every postage from 1 to n can be paid for with at most 21 stamps.

3813 is the number of partitions of 47 in which no part occurs only once.

3816 is a truncated cube number.

3822 is the number of triangles of any size contained in the triangle of side 24 on a triangular grid.

3824 is the number of lines through exactly 2 points of a 12×12 grid of points.

3825 is a Kaprekar constant in base 2.

3827 is a composite number n that divides the (n+1)^st Fibonacci number.

3829 is the sum of the first 16 numbers that have digit sum 16.

3832 is the number of fixed 6-kings.

3834 is the number of weakly connected directed graphs with 4 vertices.

3836 is the maximum number of inversions in a permutation of length 7.

3840 = 10!!.

3841 is the number of interior intersections when all the diagonals of a regular 20-gon are drawn.

3843 is a value of n for which 7n and 9n together use each digit exactly once.

3846 is the number of Hamiltonian cycles of a 4×11 rectangle graph.

3849 has a square with the first 3 digits the same as the next 3 digits.

3850 is a structured octagonal anti-diamond number.

3855 is an odd number for which a regular polygon is constructible by straightedge and compass.

3857 is the number of 6-dimentional partitions of 7.

3859 is a member of the Fibonacci-type sequence starting with 2 and 9.

3861 is the smallest number whose 4^th power starts with 5 identical digits.

3864 is a strong Friedman number.

3865 is a Smith brother.

3871 is the sum of the cubes of 3 consecutive primes.

3872 is an Achilles number.

3873 is a Kaprekar constant in base 4.

3876 = ₁₉C₄.

3882 is the sum of its proper divisors that contain the digit 4.

3883 is the smallest number whose cube contains 4 consecutive 6's.

3884 has a 5^th root that starts 5.22222....

3888 is an Achilles number.

3889 + φ(3889) = 7777.

3893 is the number of 3-regular connected planar graphs with 18 vertices.

3894 is an octahedral number.

3895 is the number of intersections when all the diagonals of a regular 19-gon are drawn.

3896 is the number of ways to place 3 non-attacking bishops on a 6×6 chessboard.

3897 divides the sum of the digits of 3897!.

3900 has a base 2 representation that is two copies of its base 5 representation concatenated.

3901 has a base 2 representation that ends with its base 5 representation.

3903 is a Lucas 7-step number.

3906 = 111111 in base 5.

3907 = 15628 / 4, and each digit is contained in the equation exactly once.

3910 is the number of 3×3 sliding puzzle positions that require exactly 28 moves to solve starting with the hole in a corner.

3911 and its reverse are prime, even if we append or prepend a 3 or 9.

3912 is a value of n for which 5n and 7n together use each digit exactly once.

3913 is a Huay rhombic dodecahedral number.

3916 is a triangular number whose internal digits are triangular and whose external digits are triangular.

3920 = (5+3) × (5+9) × (5+2) × (5+0).

3923 is a factor of 3924392539263927.

3925 is a centered cube number.

3926 is the 12^th open meandric number.

3927 has an 8^th root whose decimal part starts with the digits 1-9 in some order.

3928 is the closest integer to 21^e.

3929 is the number of integers with complexity 29.

3937 is a Kaprekar constant in base 2.

3938 is the number of 4×4 sliding puzzle positions that require exactly 11 moves to solve starting with the hole in a corner.

3939 is a structured truncated tetrahedral number.

3942 is a value of n for which n and 4n together use each digit 1-9 exactly once.

3952 has a sum of digits equal to its largest prime factor.

3956 is the number of conjugacy classes in the automorphism group of the 15 dimensional hypercube. 

3957 is the number of ways to stack 32 boxes in a line so that each box lies on the table or on a box next to 2 boxes.

3960 is a highly abundant number.

3967 is the smallest number whose 12^th power contains exactly the same digits as another 12^th power.

3968 and its successor are both divisible by 4^th powers.

3969 is a Kaprekar constant in base 2.

3972 is a strong Friedman number.

3973 has a 4^th power that is the sum of four 4^th powers.

3977 has the property that dropping its first and last digits gives its largest prime factor.

3978 is the number of ways to place 30 points on a 15×15 grid so that no 3 points are on a line.

3979 is the number of centered trees with 15 vertices.

3980 is the smallest multiple of 20 whose digits add to 20.

3982 is the smallest number whose 5^th power has 18 digits.

3983 has the property that the concatenation of its prime factors in increasing order is a square.

3984 is a Heptanacci number.

3985 = 3333 + 9 + 88 + 555.

3986 has an 8^th root that starts 2.81881881....

3987 is the closest integer to 14^π.

3991 is the number of labeled graded partially ordered sets with 5 elements.

3993 is a structured snub cubic number.

3994 is the number of transitive relations on 4 labeled nodes.

3996 = (6⁶ + 6⁷ + 6⁸ + 6⁹) / (6 × 7 × 8 × 9).

3999 is the smallest number whose digits add to 30.

4000 has a cube that contains only even digits.