Properties of the Number 21816

Twenty-One Thousand Eight Hundred Sixteen

Basics

Value: 21815 → 21816 → 21817

Parity: even

Prime: No

Previous Prime: 21803

Next Prime: 21817

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 2 ³ × 3 ³ × 101

Divisors: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010100111000

Octal: 52470

Duodecimal: 10760

Hexadecimal: 5538

Square: 475937856

Square Root: 147.70240350109404

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

a(n) = 12·a(n-1) - 30·a(n-2) with a(0)=1 and a(1)=6. A145301

Numbers of the form p³*q³*r where p, q, and r are prime. A179688

T(n,k)=Number of nXk 0..3 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of the elements above it or one plus the sum of the elements diagonally to its northwest or one plus the sum of the elements antidiagonally to its northeast, modulo 4. A240260

Inverse binomial transform of A026007. A294503

Numbers with at least two 3s in their prime signature. A109399

Expansion of 1/theta₄(q)¹² in powers of q = exp(π i t). A319554

Expansion of ( ∑_{n = -infinity..infinity} x^n² )^-12. A4413

Row sums of triangle A182701. A182705

Irregular triangle read by rows: coefficients in order of decreasing exponents of polynomials P_g(x) related to Hultman numbers. A185259

Number of 10-element subsets of [n+10] having an even sum. A282078