Properties of the Number 21500

Twenty-One Thousand Five Hundred

Basics

Value: 21499 → 21500 → 21501

Parity: even

Prime: No

Previous Prime: 21499

Next Prime: 21503

Digit Sum: 8

Digital Root: 8

Palindrome: No

Factorization: 2 ² × 5 ³ × 43

Divisors: 1, 2, 4, 5, 10, 20, 25, 43, 50, 86

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101001111111100

Octal: 51774

Duodecimal: 10538

Hexadecimal: 53fc

Square: 462250000

Square Root: 146.6287829861518

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

T(n,k)=Number of nXk 0..1 arrays with every element equal to 0, 1, 3, 4, 5, 7 or 8 king-move adjacent elements, with upper left element zero. A299886

a(n) = coefficient of xⁿ*yⁿ in ∏_n>=1 (1 - (xⁿ + yⁿ))³. A322214

a(n) = T(5,n), array T given by A047858. A47862

Number of (7+2) X (n+2) 0..1 arrays with every 3 X 3 subblock sum of the two sums of the diagonal and antidiagonal minus the two minimums of the central column and central row nondecreasing horizontally, vertically and ne-to-sw antidiagonally. A254913

Number of n X 4 0..1 arrays with every element equal to 0, 1, 3, 4, 5, 7 or 8 king-move adjacent elements, with upper left element zero. A299882

Number of nX7 0..1 arrays with every element equal to 0, 1, 3, 4, 5, 7 or 8 king-move adjacent elements, with upper left element zero. A299885

Numbers n such that (digital sum of n)³ = reversal of n. (Powers of 10 excluded.) A85754

Number of walks within N³ (the first octant of Z³) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, -1, 1), (-1, 1, -1), (0, 0, 1), (1, 0, -1)}. A148004

a(n) is the least number k such that the continued fraction of the abundancy index of k contains n elements that are all distinct, or -1 if no such k exists. A349691

a(n) = length (or lifetime) of the meta-Fibonacci sequence {f(1) = ... = f(n) = 1; f(k)=f(k-f(k-1))+f(k-f(k-n))} if that sequence is only defined for finitely many terms, or 0 if that sequence is infinite. A134680