Properties of the Number 21390

Twenty-One Thousand Three Hundred Ninety

Basics

Value: 21389 → 21390 → 21391

Parity: even

Prime: No

Previous Prime: 21383

Next Prime: 21391

Digit Sum: 15

Digital Root: 6

Palindrome: No

Factorization: 2 × 3 × 5 × 23 × 31

Divisors: 1, 2, 3, 5, 6, 10, 15, 23, 30, 31

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 101001110001110

Octal: 51616

Duodecimal: 10466

Hexadecimal: 538e

Square: 457532100

Square Root: 146.25320509308506

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(n, k, m) = (m*(n-k) + 1)*T(n-1, k-1, m) + (m·k + 1)*T(n-1, k, m) + m·f(n,k)*T(n-2, k-1, m) with T(n, 0, m) = T(n, n, m) = 1, f(n, k) = k if k <= floor(n/2) otherwise n-k, and m = 1, read by rows. A157207

Triangle read by rows: T(n,k) is the number of deco polyominoes of height n and having k 2-cell columns (n>=1; 0<=k<=n-1). A deco polyomino is a directed column-convex polyomino in which the height, measured along the diagonal, is attained only in the last column. A121637

Number of partitions satisfying 0 < cn(1,5) + cn(2,5) + cn(3,5) and 0 < cn(4,5) + cn(2,5) + cn(3,5). A39901

a(n) = (1/4)*(n² - 2·n)² + (9/4)*(n² - 2·n) + 6. A294070

Sum of the areas of the distinct rectangles (and the areas of the squares on their sides) with positive integer sides such that L + W = n, W < L. A294139

Maximum size of a class of binary words of length n having the same prefix normal form. A238110

Decimal expansion of 1/386. A21390