Properties of the Number 21156

Twenty-One Thousand One Hundred Fifty-Six

Basics

Value: 21155 → 21156 → 21157

Parity: even

Prime: No

Previous Prime: 21149

Next Prime: 21157

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 2 ² × 3 × 41 × 43

Divisors: 1, 2, 3, 4, 6, 12, 41, 43, 82, 86

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 101001010100100

Octal: 51244

Duodecimal: 102B0

Hexadecimal: 52a4

Square: 447576336

Square Root: 145.45102268461366

Classification

Fibonacci: No

Bell Number: No

Factorial Number: No

Regular Number: No

Perfect Number: No

Special

Kaprekar Constant: No

Munchausen Constant: No

Armstrong Number: No

Kaprekar Number: No

Catalan Number: No

Vampire Number: No

Taxicab Number: No

Super Prime: No

Friedman Number: No

Fermat Number: No

Cullen Number: No

OEIS Sequences

Number of pentagonal regions in regular n-gon with all diagonals drawn. A67152

Expansion of 1/∏_m>=1 (1 - m·q^m)¹². A22736

Symmetric square table of coefficients, read by antidiagonals, where T(n,k) is the coefficient of xⁿ*y^k in f(x,y) that satisfies f(x,y) = (1-xy)/[(1-x)(1-y)] + xy·f(x,y)³. A86626

Fixed points of A300956. A300958

Numbers k that divide the (right) concatenation of all numbers <= k written in base 3 (most significant digit on left). A29448

Number of arrangements of 4 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero. A188250

Rank of the inverse semigroup D_n of all difunctional relations on an n-element set. A294431

Triangle read by rows: T(n,k) (0 <= k <= n) is the rank of the ideal I_r in the inverse semigroup D_n of all difunctional relations on an n-element set. A294432

Numbers k such that prime(k+1)^prime(k+3) == prime(k) mod prime(k+2). A335571

Numbers k such that 2·R_k + 3·10^k + 1 is prime, where R_k = 11...11 is the repunit (A002275) of length k. A259129