Properties of the Number 21931

Twenty-One Thousand Nine Hundred Thirty-One

Basics

Value: 21930 → 21931 → 21932

Parity: odd

Prime: No

Previous Prime: 21929

Next Prime: 21937

Digit Sum: 16

Digital Root: 7

Palindrome: No

Factorization: 7 × 13 × 241

Divisors: 1, 7, 13, 91, 241, 1687, 3133, 21931

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010110101011

Octal: 52653

Duodecimal: 10837

Hexadecimal: 55ab

Square: 480968761

Square Root: 148.09118812407442

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

Numbers m such that the factorizations of m..m+4 have the same number of primes (including multiplicities). A45941

Number of rational knots (or two-bridge knots) with n crossings (up to mirroring). A18240

Square loops: the number of circular permutations (reversals not counted as different) of the numbers 1 to n such that the sum of any two consecutive numbers is a square. A71984

a(n) = 12·n² + 18·n + 7. A154105

Strong pseudoprimes to base 10. A20236

Deceptive nonprimes: composite numbers k that divide the repunit R_k-1. A864

Gaps of 6 in sequence A038593 (upper terms). A38652

Number of (w,x,y) with all terms in {0,...,n} and 2·max(w,x,y) >= 3·min(w,x,y). A213392

Odd numbers k such that A064989(k) is in A340151. A340091

a(n) = (1ⁿ + (-2)ⁿ + 4ⁿ)/3. A245489