Properties of the Number 21480

Twenty-One Thousand Four Hundred Eighty

Basics

Value: 21479 → 21480 → 21481

Parity: even

Prime: No

Previous Prime: 21467

Next Prime: 21481

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 2 ³ × 3 × 5 × 179

Divisors: 1, 2, 3, 4, 5, 6, 8, 10, 12, 15

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 101001111101000

Octal: 51750

Duodecimal: 10520

Hexadecimal: 53e8

Square: 461390400

Square Root: 146.56056768449008

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 regions in regular n-gon with all diagonals drawn. A7678

Numbers k such that k! - 1 is prime. A2982

Number of oriented graphs (i.e., digraphs with no bidirected edges) on n unlabeled nodes. Also number of complete digraphs on n unlabeled nodes. Number of antisymmetric relations (i.e., oriented graphs with loops) on n unlabeled nodes is A083670. A1174

Array read by antidiagonals: T(n,k) = number of n-step knight's tours on a (k+2)X(k+2) board summed over all starting positions. A186851

Total number of parts in all partitions of n with at least one distinct part. A220477

Expansion of ∏_k>=1 1/((1 - x^k) * (1 - x^2·k) * (1 - x^3·k) * (1 - x^4·k) * (1 - x^5·k)). A327044

dot_product(n,n-1,...2,1)*(7,8,...,n,1,2,3,4,5,6). A26066

Number T(n,k) of sets of nonempty words with a total of n letters over k-ary alphabet such that for k>0 the k-th letter occurs at least once and within each word every letter of the alphabet is at least as frequent as the subsequent alphabet letter; triangle T(n,k), n>=0, 0<=k<=n, read by rows. A319498

Place two n-gons with radii 1 and 2 concentrically, forming an annular area between them. Connect all the vertices with line segments that lie entirely within that area. Then a(n) is the number of regions in that figure. A337700

Number of 5-step knight's tours on an (n+2) X (n+2) board summed over all starting positions. A186854