Properties of the Number 31781

Thirty-One Thousand Seven Hundred Eighty-One

Basics

Value: 31780 → 31781 → 31782

Parity: odd

Prime: No

Previous Prime: 31771

Next Prime: 31793

Digit Sum: 20

Digital Root: 2

Palindrome: No

Factorization: 61 × 521

Divisors: 1, 61, 521, 31781

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 111110000100101

Octal: 76045

Duodecimal: 16485

Hexadecimal: 7c25

Square: 1010031961

Square Root: 178.27226368675525

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(0)=0, a(1)=1, a(2)=2; for n > 2, a(n) = 3·a(n-1) - a(n-2) - 2·a(n-3). A27934

Expansion of x/((1-x-x³)*(1-x)⁵). A144899

Triangle read by rows, a generalization of the Eulerian numbers based on Nielsen's generalized polylogarithm (case m = 2). A142249

Matrix square of triangle A063967. A91700

[s(k)-s(j)]/10, where the pairs (k,j) are given by A205877 and A205878, and s(k) denotes the (k+1)-st Fibonacci number. A205880

Positions of records in A096303. A229743

Semiprimes generated by the polynomial 2·n² + 29. A241554

a(n) = 5·3ⁿ - 4·2ⁿ. A102485

Composite numbers of the form 2·k² + 29. A352949

a(n) = 10000·log(n) rounded to nearest integer. A4244