Properties of the Number 21540

Twenty-One Thousand Five Hundred Forty

Basics

Value: 21539 → 21540 → 21541

Parity: even

Prime: No

Previous Prime: 21529

Next Prime: 21557

Digit Sum: 12

Digital Root: 3

Palindrome: No

Factorization: 2 ² × 3 × 5 × 359

Divisors: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20

Polygonal

Triangular: No

Square: No

Pentagonal: Yes

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101010000100100

Octal: 52044

Duodecimal: 10570

Hexadecimal: 5424

Square: 463971600

Square Root: 146.76511847165867

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) = n*(n + 1)*(3·n² + 3·n - 2)/8. A236770

Number of partitions into one kind of 1's, two kinds of 2's, and three kinds of 3's. A2597

Numbers which are the sum of their proper divisors containing the digit 7. A59466

Least integer m > 0 with π(m·n) = σ(m) + σ(n), where π(.) and σ(.) are given by A000720 and A000203 respectively. A247673

Prime sieve of e. A248804

Triangle read by rows: T(n,k) is the number of digraphs on n labeled nodes with k arcs and a global source (or sink), n >= 1, k = 0..(n-1)². A350793

Pentagonal numbers that are abundant. A379264

Numbers n such that [A070080(n), A070081(n), A070082(n)] is an isosceles integer triangle with integer area. A70145

a(n) = 3·n*(9·n - 1)/2. A268351

a(n) = a(n-1) + 3·a(n-2) - 2·a(n-3) - a(n-4) for n >= 4, where a(0) = 2, a(1) = 4, a(2) = 7, a(3) = 12. A288317