Properties of the Number 21997

Twenty-One Thousand Nine Hundred Ninety-Seven

Basics

Value: 21996 → 21997 → 21998

Parity: odd

Prime: Yes

Previous Prime: 21991

Next Prime: 22003

Digit Sum: 28

Digital Root: 1

Palindrome: No

Factorization: 21997

Divisors: 1, 21997

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010111101101

Octal: 52755

Duodecimal: 10891

Hexadecimal: 55ed

Square: 483868009

Square Root: 148.3138563991915

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

Primes p for which the period of reciprocal 1/p is (p-1)/12. A56217

T(n,k)=Number of (n+1)X(k+1) arrays of permutations of 0..(n+1)*(k+1)-1 with each element having directed index change 0,0 0,1 1,0 -1,0 or 0,-2. A264217

Smaller member p of a pair (p,p+6) of consecutive primes in different centuries. A160370

Primes that remain prime through 3 iterations of function f(x) = 5x + 2. A23283

Primes that remain prime through 4 iterations of function f(x) = 5x + 2. A23313

G.f. satisfies A(x) = 1 + x⁵ / (1 - x·A(x)). A365698

Number of lines through at least 2 points of a 10 X n grid of points. A160850

Primes of the form floor(binomial(k,2)/4). A171574

Square array read by antidiagonals upwards: M(n,k) is the initial occurrence of first prime p1 of consecutive primes p1, p2, where p2 - p1 = 2·k, and p1, p2 span a multiple of 10ⁿ, n>=1, k>=1. A287050

Primes p such that the multiplicative order of 2 modulo p is (p-1)/9. A152309