Properties of the Number 21921

Twenty-One Thousand Nine Hundred Twenty-One

Basics

Value: 21920 → 21921 → 21922

Parity: odd

Prime: No

Previous Prime: 21911

Next Prime: 21929

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 3 × 7307

Divisors: 1, 3, 7307, 21921

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 101010110100001

Octal: 52641

Duodecimal: 10829

Hexadecimal: 55a1

Square: 480530241

Square Root: 148.05742129322664

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

a(n) = least k such that the remainder when 28^k is divided by k is n. A128368

a(n) is the sum of the digits of the squares of all n-digit numbers. A333034

Expansion of a modular function for Gamma₀(15). A2510

Indices of primes in sequence defined by A(0) = 91, A(n) = 10·A(n-1) + 31 for n > 0. A101006

Numbers n which are both happy (A007770) and bihappy (A257795) numbers. A257950

Number of nX6 0..1 arrays with every element equal to 0, 1, 3, 5, 6 or 8 king-move adjacent elements, with upper left element zero. A299449

Concatenations C1 and C2 and C3 are all prime (see the comment lines). A34817

T(n,k)=Number of nXk 0..1 arrays with every element equal to 0, 1, 3, 5, 6 or 8 king-move adjacent elements, with upper left element zero. A299451

Expansion of -x·d(log((1-x*(2/sqrt(3·x)) * sin((1/3) * arcsin(sqrt(27·x/4))))))/dx. A242798

A number k is included if at least one prime dividing k is equal to an exponent of the highest power of any prime dividing k. A111371