Properties of the Number 20906

Twenty Thousand Nine Hundred Six

Basics

Value: 20905 → 20906 → 20907

Parity: even

Prime: No

Previous Prime: 20903

Next Prime: 20921

Digit Sum: 17

Digital Root: 8

Palindrome: No

Factorization: 2 × 10453

Divisors: 1, 2, 10453, 20906

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101000110101010

Octal: 50652

Duodecimal: 10122

Hexadecimal: 51aa

Square: 437060836

Square Root: 144.58907289280197

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

Number of permutations p of 1,2,...,n satisfying p(i+2) - p(i) <> 2 for all 1 <= i <= n-2. A189281

Number of subsets of [n] avoiding 3-term arithmetic progressions and containing n if n>0. A334893

p-INVERT of (1,2,3,5,7,11,13,...); i.e., 1 and the primes (A008578), where p(S) = 1 - S - S². A289928

Number of length n+4 0..5 arrays with every five consecutive terms having four times some element equal to the sum of the remaining four. A249653

G.f. A(x) satisfies A(x) = 1 + x / (1 - x·A(x)²)⁴. A378733

Multiplicity of highest weight (or singular) vectors associated with character chi₁₁₅ of Monster module. A34503

Numbers k such that 273·2^k-1 is prime. A50895

Triangle where n-th row is the first n terms of the sequence in reverse order, starting with a(1) = 1 and a(2) = 2. A20906

Number of nX4 0..1 arrays with every element equal to 2, 3, 5 or 6 king-move adjacent elements, with upper left element zero. A298083