Properties of the Number 19780

Nineteen Thousand Seven Hundred Eighty

Basics

Value: 19779 → 19780 → 19781

Parity: even

Prime: No

Previous Prime: 19777

Next Prime: 19793

Digit Sum: 25

Digital Root: 7

Palindrome: No

Factorization: 2 ² × 5 × 23 × 43

Divisors: 1, 2, 4, 5, 10, 20, 23, 43, 46, 86

Polygonal

Triangular: No

Square: No

Pentagonal: Yes

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2196 Try Today's Challenge

Representations

Binary: 100110101000100

Octal: 46504

Duodecimal: B544

Hexadecimal: 4d44

Square: 391248400

Square Root: 140.64138793399331

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 of partitions of n with equal number of even and odd parts. A45931

Numbers n such that σ(n) = 6*φ(n). A104900

A(n,k) is (1/k) times the number of n-member subsets of [k·n] whose elements sum to a multiple of n; square array A(n,k), n>=1, k>=1, read by antidiagonals. A309148

Dirichlet convolution of 3^n-1 with φ(n). A34754

Irregular table read by rows: n-th row lists the 9 n-gonal numbers of a 3 X 3 semimagic square with the smallest magic sum. The terms of each row are arranged in the manner shown in A261816. A265141

Pentagonal numbers (A000326) whose digit reversal is a semiprime (A001358). A115709

Composite numbers with properties that its digits (which may appear with multiplicity) may not appear in any of its factors (wherein the digits may also appear with multiplicity) and the combined digits of the product and the factors must have at least one of each of the ten digits. A370972

Expansion of ∏_k>=1 1/(1 - x^2·k+1)^2·k+1. A263199

Decimal representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 358", based on the 5-celled von Neumann neighborhood. A287784

Numbers k such that 1 + 2^k*k³ is prime. A357612