Properties of the Number 21756

Twenty-One Thousand Seven Hundred Fifty-Six

Basics

Value: 21755 → 21756 → 21757

Parity: even

Prime: No

Previous Prime: 21751

Next Prime: 21757

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 2 ² × 3 × 7 ² × 37

Divisors: 1, 2, 3, 4, 6, 7, 12, 14, 21, 28

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101010011111100

Octal: 52374

Duodecimal: 10710

Hexadecimal: 54fc

Square: 473323536

Square Root: 147.49915253993834

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

Triangle T(m,k) read by rows, where T(m,k) is the number of ways in which 1<=k<=m positions can be picked in an m X m square grid such that the picked positions have a point symmetry or a line symmetry. A292153

a(n) = 25·n² + 25·n + 6. A177059

Consider Watanabe's 3-shift tag system {00/1011} applied to the word (100)ⁿ; a(n) = position of the longest word in the orbit, or -1 if the orbit is unbounded. A292094

Sum of the elements in the coprime subsets of the integers 1 to n. A87081

a(n) = 4·n*(4·n - 1). A104188

Volume of the 3-dimensional box of sides of length equal to consecutive Padovan numbers (A000931). These boxes form a spiral in three dimensions similar to the spiral of Fibonacci boxes in two dimensions. A100538

Number of partitions of n into distinct parts with boundary size 8. A227565

v(n+1)/v(n), where v=A203012. A203158

Array read by antidiagonals: T(n,k) = number of lattice paths from (0,0) to (n,k) using steps (1,0), (0,1), (1,1), (-1,1) and whose points lie entirely in the integer rectangle of lattice points {(i, j): 0 <= i <= n, 0 <= j <= k}. A232968

Least integer k > 1 such that π(k)² + π(k·n)² is a square, where π(.) is the prime-counting function given by A000720. A255677