Properties of the Number 18720

Eighteen Thousand Seven Hundred Twenty

Basics

Value: 18719 → 18720 → 18721

Parity: even

Prime: No

Previous Prime: 18719

Next Prime: 18731

Digit Sum: 18

Digital Root: 9

Palindrome: No

Factorization: 2 ⁵ × 3 ² × 5 × 13

Divisors: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

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Representations

Binary: 100100100100000

Octal: 44440

Duodecimal: AA00

Hexadecimal: 4920

Square: 350438400

Square Root: 136.82105101189657

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 double-free subsets of {1, 2, ..., n}. A50291

Strongly refactorable numbers: numbers n such that if n is divisible by d, it is divisible by the number of divisors of d. A141586

Number A(n,k) of permutations of k indistinguishable copies of 1..n with every partial sum <= the same partial sum averaged over all permutations; square array A(n,k), n>=0, k>=0, read by antidiagonals. A215561

Smallest k such that σ(x) = k has exactly n solutions. A7368

When expressed in base 3 and then interpreted in base 8, is a multiple of the original number. A62889

Numbers k that, when expressed in base 5 and then interpreted in base 8, give a multiple of k. A62930

Numbers k which have a factorization k = f1·f2*...*fr where the digits of {k, f1, f2, ..., fr} together give 0,1,...,9 exactly once. A370970

Let sigma_m (n) be result of applying sum-of-divisors function m times to n; call n (m,k)-perfect if sigma_m (n) = k·n; sequence gives the (4,k)-perfect numbers. A19293

G.f. satisfies A(x) = 1 + x*(1 + x·A(x)⁶)⁴. A137971

a(n) = ∑_d∣n Moebius(n/d)*d^b-1/φ(n) for b = 5. A160891