Properties of the Number 21945

Twenty-One Thousand Nine Hundred Forty-Five

Basics

Value: 21944 → 21945 → 21946

Parity: odd

Prime: No

Previous Prime: 21943

Next Prime: 21961

Digit Sum: 21

Digital Root: 3

Palindrome: No

Factorization: 3 × 5 × 7 × 11 × 19

Divisors: 1, 3, 5, 7, 11, 15, 19, 21, 33, 35

Polygonal

Triangular: Yes

Square: No

Pentagonal: No

Hexagonal: Yes

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 101010110111001

Octal: 52671

Duodecimal: 10849

Hexadecimal: 55b9

Square: 481583025

Square Root: 148.13844875656017

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

Tritriangular numbers: a(n) = binomial(binomial(n,2),2) = n*(n+1)*(n-1)*(n-2)/8. A50534

Odd primitive abundant numbers. A6038

a(n) = n⁴ - (n-1)⁴ + (n-2)⁴ - ... 0⁴. A62392

One third of quartic factorial numbers. A34176

Odd infinitary abundant numbers. A127666

Odd unitary abundant numbers. A129485

Odd bi-unitary abundant numbers: odd numbers k such that bsigma(k) > 2·k, where bsigma is the sum of the bi-unitary divisors function (A188999). A293186

Odd squarefree abundant numbers. A112643

Expansion of g.f. x*(1 + x)*(1 + 6·x + x²)/(1 - x)⁷. A6858

Primitive, odd, squarefree abundant numbers. A249263