Properties of the Number 21008

Twenty-One Thousand Eight

Basics

Value: 21007 → 21008 → 21009

Parity: even

Prime: No

Previous Prime: 21001

Next Prime: 21011

Digit Sum: 11

Digital Root: 2

Palindrome: No

Factorization: 2 ⁴ × 13 × 101

Divisors: 1, 2, 4, 8, 13, 16, 26, 52, 101, 104

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001000010000

Octal: 51020

Duodecimal: 101A8

Hexadecimal: 5210

Square: 441336064

Square Root: 144.9413674559475

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

Expansion of (theta₃(z)*theta₃(23z)+theta₂(z)*theta₂(23z))⁴. A28660

a(n) is the smallest number which can be represented as the sum of n distinct nonzero squares in exactly 2 ways, or -1 if no such number exists. A374287

Irregular triangular array T; row n shows the coefficients of the (n-1)-st polynomial in the obverse convolution s(x)**t(x), where s(x) = n² x and t(x) = x+2. See Comments. A375043

Number of permutations p of [n] such that p(i) > p(i+1) iff i == 1 (mod 7). A250263

Number of -3..3 arrays x(i) of n+1 elements i=1..n+1 with set{t,u,v in 0,1}((x[i+t]+x[j+u]+x[k+v])*(-1)^t+u+v) having three, four or five distinct values for every i,j,k<=n. A211724

Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 401", based on the 5-celled von Neumann neighborhood. A271805

Number of strictly recursively normal integer partitions of n. A330937

Expansion of (1/x) * Series_Reversion( x * (1+x)³ / (1+x+x²)⁴ ). A372383

Companion Pell numbers: a(n) = 2·a(n-1) + a(n-2), a(0) = a(1) = 2. A2203

Pisot sequence P(5,11), a(0)=5, a(1)=11, a(n+1) is the nearest integer to a(n)²/a(n-1). A21008