Properties of the Number 21957

Twenty-One Thousand Nine Hundred Fifty-Seven

Basics

Value: 21956 → 21957 → 21958

Parity: odd

Prime: No

Previous Prime: 21943

Next Prime: 21961

Digit Sum: 24

Digital Root: 6

Palindrome: No

Factorization: 3 × 13 × 563

Divisors: 1, 3, 13, 39, 563, 1689, 7319, 21957

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 101010111000101

Octal: 52705

Duodecimal: 10859

Hexadecimal: 55c5

Square: 482109849

Square Root: 148.17894587288708

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

T(n,k)=Number of (n+1)X(k+1) 0..1 arrays x(i,j) with row sums sum{x(i,j), j=1..k+1} nondecreasing, and column sums sum{i²*x(i,j), i=1..n+1} nondecreasing. A233301

Numbers that are the sum of eight fourth powers in nine or more ways. A345584

Numbers that are the sum of eight fourth powers in ten or more ways. A345585

a(n) = n³ + 5. A84381

Numbers k such that 31·2^k-1 is prime. A50541

Last term where no prime sums occur in A161190 in a 4-diagonal set of 24 terms. A161193

Number of (4+1) X (n+1) 0..1 arrays x(i,j) with row sums sum{x(i,j), j=1..n+1} nondecreasing, and column sums sum{i²*x(i,j), i=1..4+1} nondecreasing. A233304

a(n) is the smallest integer >= a(n-1) such that prime(n)*2^a(n)-1 is a prime number. A258868

Expansion of 1/(1 - ∑_k>=2 floor(bigomega(k)/2)*floor(2/bigomega(k))*x^k), where bigomega(k) is the number of prime divisors of k counted with multiplicity (A001222). A280238

Number of walks within N³ (the first octant of Z³) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 1, 1), (0, 0, -1), (1, 0, -1), (1, 1, 1)}. A149690