Properties of the Number 81690

Eighty-One Thousand Six Hundred Ninety

Basics

Value: 81689 → 81690 → 81691

Parity: even

Prime: No

Previous Prime: 81689

Next Prime: 81701

Digit Sum: 24

Digital Root: 6

Palindrome: No

Factorization: 2 × 3 × 5 × 7 × 389

Divisors: 1, 2, 3, 5, 6, 7, 10, 14, 15, 21

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 10011111100011010

Octal: 237432

Duodecimal: 3B336

Hexadecimal: 13f1a

Square: 6673256100

Square Root: 285.8146252381078

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 T(n,k) of sets of exactly k nonempty words with a total of n letters over n-ary alphabet such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter; triangle T(n,k), n>=0, read by rows. A293815

a(n) = [xⁿ] (1 + x*(1+x)ⁿ⁺¹ )ⁿ⁺¹. A121680

Numbers k having exactly 5 distinct prime factors, the largest of which is greater than or equal to sqrt(k) (i.e., sqrt(k)-rough numbers with exactly 5 distinct prime factors). A115959

Triangle T(n,k) of series-reduced (or homeomorphically irreducible) labeled graphs with n nodes and k edges, k=0..binomial(n,2). A60514

Array: row n shows the coefficients of the characteristic polynomial of the n-th principal submatrix of the symmetric matrix A203003; by antidiagonals. A203004

Number of sets of exactly two nonempty words with a total of n letters over n-ary alphabet such that within each prefix of a word every letter of the alphabet is at least as frequent as the subsequent alphabet letter. A293964

A binomial conjugate of the Narayana numbers. A177896

From P-positions in a certain game. A81690