Properties of the Number 21979

Twenty-One Thousand Nine Hundred Seventy-Nine

Basics

Value: 21978 → 21979 → 21980

Parity: odd

Prime: No

Previous Prime: 21977

Next Prime: 21991

Digit Sum: 28

Digital Root: 1

Palindrome: No

Factorization: 31 × 709

Divisors: 1, 31, 709, 21979

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101010111011011

Octal: 52733

Duodecimal: 10877

Hexadecimal: 55db

Square: 483076441

Square Root: 148.25316185498372

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

Partial sums of A008137. A299276

a(0) = -1, a(1) = 2; a(n) = 2·a(n-1) + a(n-2). A78343

2·a(n)² + 7 is a square. A77442

Part of the y solutions of the Pell equation x² - 2·y² = +7. A253811

Fixed-k dispersion for Q = 8: Square array D(g,h) (g, h >= 1), read by ascending antidiagonals. A120861

Numbers which are the sum of two positive cubes and divisible by 31. A102658

Start with the sequence S(0)={1,1} and for k>0 define S(k) to be I(S(k-1)) where I denotes the operation of inserting, for i=1,2,3..., the term a(i)+a(i+1) between any two terms for which 4a(i+1)<=5a(i). The listed terms are the initial terms of the limit of this process as k goes to infinity. A82981

a(n) = n·prime(prime(n)). A80697

Semiprimes in A054567. A113692

a(n) = 2·a(n - 2) + a(n - 4) with a(0) = a(1) = 2, a(2) = 1, a(3) = 3. A266504