Properties of the Number 21666

Twenty-One Thousand Six Hundred Sixty-Six

Basics

Value: 21665 → 21666 → 21667

Parity: even

Prime: No

Previous Prime: 21661

Next Prime: 21673

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 2 × 3 × 23 × 157

Divisors: 1, 2, 3, 6, 23, 46, 69, 138, 157, 314

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101010010100010

Octal: 52242

Duodecimal: 10656

Hexadecimal: 54a2

Square: 469415556

Square Root: 147.19374986730924

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 partitions with no even part repeated; partitions of n in which no parts are multiples of 4. A1935

Expansion of ψ(x) / φ(x) in powers of·where φ(), ψ() are Ramanujan θ functions. A83365

53 'Reverse and Add' steps are needed to reach a palindrome. A65320

Number of partitions of 2n in which no parts are multiples of 4. A81055

G.f. satisfies A(x) = 1 / (1 - x²*A(x)² / (1 - x)). A376489

Numbers k such that k+1 is composite and divides 3^k-2^k. A68410

Expansion of g.f. x*(1-x+x⁵+x⁶-x⁷+x⁹)/(1-2·x+x⁴+x⁶-2·x⁷+x¹⁰). A97596

Number of (n+1)X5 0..1 arrays with the number of rightwards and downwards edge increases in each 2X2 subblock differing from the number in all its horizontal and vertical neighbors. A205068

Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 147", based on the 5-celled von Neumann neighborhood. A270292

Number of "coherent" reduced decompositions for the longest permutation n n-1 n-2 ... 3 2 1 in the symmetric group on n letters. A14982