Properties of the Number 21901

Twenty-One Thousand Nine Hundred One

Basics

Value: 21900 → 21901 → 21902

Parity: odd

Prime: No

Previous Prime: 21893

Next Prime: 21911

Digit Sum: 13

Digital Root: 4

Palindrome: No

Factorization: 11 ² × 181

Divisors: 1, 11, 121, 181, 1991, 21901

Polygonal

Triangular: No

Square: No

Pentagonal: Yes

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010110001101

Octal: 52615

Duodecimal: 10811

Hexadecimal: 558d

Square: 479653801

Square Root: 147.98986451781082

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(1)=3; for n > 1, a(n) = 1 + a(n-1) + gcd( a(n-1)*(a(n-1)+2), A073829(a(n-1)) ). A167053

Pentagonal numbers (A000326) which are the sum of 2 other positive pentagonal numbers. A136117

a(n) = n²*(3·n² - 1)/2. A260810

G.f. satisfies: A(x) = exp( ∑_n>=1 xⁿ/n * ∏_k>=1 (1 + x^n·k*A(x^k)ⁿ) ). A218552

Irregular table whose rows list the nontrivial cycles of the ghost iteration A329201, starting with the smallest member. A329342

E.g.f.: ∑_n>=0 (3ⁿ*x + LambertW(x))ⁿ / n!. A386656

Composite numbers whose prime factors contain no digits other than 1 and 8. A36308

Number of distinct differences between consecutive divisors of n! (ordered by size). A60737

Pentagonal numbers (A000326) that are the product of 2 palindromes greater than 1. A115745

Strong pseudoprimes to base 27. A20253