Properties of the Number 21856

Twenty-One Thousand Eight Hundred Fifty-Six

Basics

Value: 21855 → 21856 → 21857

Parity: even

Prime: No

Previous Prime: 21851

Next Prime: 21859

Digit Sum: 22

Digital Root: 4

Palindrome: No

Factorization: 2 ⁵ × 683

Divisors: 1, 2, 4, 8, 16, 32, 683, 1366, 2732, 5464

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010101100000

Octal: 52540

Duodecimal: 10794

Hexadecimal: 5560

Square: 477684736

Square Root: 147.83774890061062

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

Octahedral numbers: a(n) = n*(2·n² + 1)/3. A5900

T(n,k)=Number of (n+1)X(k+1) 0..1 arrays x(i,j) with row sums sum{x(i,j), j=1..k+1} nondecreasing, and column sums sum{i²*x(i,j), i=1..n+1} nondecreasing. A233301

Number of nonisomorphic circulant tournaments, i.e., Cayley tournaments for cyclic group of order 2n-1. A49288

a(n) = (2·8ⁿ + 2ⁿ)/3. A82412

Expansion of 1/sqrt(1-16x-16x²). A106260

Number of circulant tournaments on 2n+1 nodes up to Cayley isomorphism. A2086

Last occurrence of n partitions in A204814. A205301

Table read by downward antidiagonals: T(n,k) is the number of tilings of the n X k cylinder up to horizontal and vertical reflections by an asymmetric tile. A368257

a(n) is the number of positive integers k for which ∑_i=1..r p_i = ∑_i=1..r e_i = n, where p₁^e_1*...*p_r^e_r is the canonical prime factorization of k. A390784

The second Zagreb index of the Aztec diamond AZ(n) (see the Ramanes et al. reference, Theorem 2.2). A292345