Properties of the Number 21806

Twenty-One Thousand Eight Hundred Six

Basics

Value: 21805 → 21806 → 21807

Parity: even

Prime: No

Previous Prime: 21803

Next Prime: 21817

Digit Sum: 17

Digital Root: 8

Palindrome: No

Factorization: 2 × 10903

Divisors: 1, 2, 10903, 21806

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010100101110

Octal: 52456

Duodecimal: 10752

Hexadecimal: 552e

Square: 475501636

Square Root: 147.6685477683044

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

Maximal number of regions into which 4-space can be divided by n hyperspheres. A59173

Numbers k such that 297·2^k-1 is prime. A50907

a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 5, with initial values 1,-1,1,1. A25278

Number of 0..3 colorings of a 3X(n+1) array circular in the n+1 direction with new values 0..3 introduced in row major order. A214114

Decimal expansion of 1/802. A21806

a(n) = ∑_{k = 0..n} binomial(n, k)²*binomial(n+k, k)*A108625(n, k). A376461