Properties of the Number 21520

Twenty-One Thousand Five Hundred Twenty

Basics

Value: 21519 → 21520 → 21521

Parity: even

Prime: No

Previous Prime: 21517

Next Prime: 21521

Digit Sum: 10

Digital Root: 1

Palindrome: No

Factorization: 2 ⁴ × 5 × 269

Divisors: 1, 2, 4, 5, 8, 10, 16, 20, 40, 80

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010000010000

Octal: 52020

Duodecimal: 10554

Hexadecimal: 5410

Square: 463110400

Square Root: 146.696966567138

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) = 2·a(n-1) + 6·a(n-2), a(0) = 0, a(1) = 1. A83099

Intrinsic 10-palindromes: n is an intrinsic k-palindrome if it is a k-digit palindrome in some base. A60947

In the "3x+1" problem, let 0 denote a halving step and 1 denote an x->3x+1 step. Then a(n) is obtained by writing the sequence of steps needed to reach 1 from 2n+1 and reading it as a decimal number. A125710

Pseudo-random numbers: Davenport's generator for 32-bit integers. A84277

Let b(0)=1; b(1)=1; b(n+2) = (π²/6 + 6/π²)*b(n+1) - b(n). a(n) = floor(b(n)). A93607

a(n) = A000695(A014486(n)). A83931

Even integers k such that λ(sum of even divisors of k) = sum of odd divisors of k. A293356

a(n) is the least number that reaches 1 after n iterations of the infinitary totient function A064380. A362025

Numbers k such that 153·2^k-1 is prime. A50618

Sequence arising from the factorization of F(n)= A083099(n) and L(n)= A127226(n). A127607