Properties of the Number 21845

Twenty-One Thousand Eight Hundred Forty-Five

Basics

Value: 21844 → 21845 → 21846

Parity: odd

Prime: No

Previous Prime: 21841

Next Prime: 21851

Digit Sum: 20

Digital Root: 2

Palindrome: No

Factorization: 5 × 17 × 257

Divisors: 1, 5, 17, 85, 257, 1285, 4369, 21845

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010101010101

Octal: 52525

Duodecimal: 10785

Hexadecimal: 5555

Square: 477204025

Square Root: 147.80054127099805

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

Jacobsthal sequence (or Jacobsthal numbers): a(n) = a(n-1) + 2·a(n-2), with a(0) = 0, a(1) = 1; also a(n) = nearest integer to 2ⁿ/3. A1045

a(2n) = 2·a(2n-1), a(2n+1) = 2·a(2n)+1 (also a(n) is the n-th number without consecutive equal binary digits). A975

a(n) = (4ⁿ - 1)/3. A2450

Sierpiński's triangle (Pascal's triangle mod 2) converted to decimal. A1317

Expansion of 1/((1-x)*(1+2·x)). A77925

Dispersion of A016813 (4k+1, k>1), by antidiagonals. A191667

a(n) = C(n,0) + C(n,3) + ... + C(n,3[n/3]). A24493

a(n) is the index of F(n+1) at the unique occurrence of the ordered pair of reversed consecutive terms (F(n+1),F(n)) in Stern's diatomic sequence A002487, where F(k) denotes the k-th term of the Fibonacci sequence A000045. A86893

Triangle of Gaussian binomial coefficients [ n,k ] for q = 4. A22168

One-dimensional cellular automaton 'σ-minus' (Rule 90): 000,001,010,011,100,101,110,111 -> 0,1,0,1,1,0,1,0. A38183