Properties of the Number 80

Eighty

Basics

Value: 79 → 80 → 81

Parity: even

Prime: No

Previous Prime: 79

Next Prime: 83

Digit Sum: 8

Digital Root: 8

Palindrome: No

Factorization: 2 ⁴ × 5

Divisors: 1, 2, 4, 5, 8, 10, 16, 20, 40, 80

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

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Representations

Binary: 1010000

Octal: 120

Duodecimal: 68

Hexadecimal: 50

Square: 6400

Square Root: 8.94427190999916

Classification

Fibonacci: No

Bell Number: No

Factorial Number: No

Regular Number: Yes

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(n) = σ(n), the sum of the divisors of n. Also called sigma₁(n). A203

a(n) = n' = arithmetic derivative of n: a(0) = a(1) = 0, a(prime) = 1, a(m·n) = m·a(n) + n·a(m). A3415

The composite numbers: numbers n of the form x·y for x > 1 and y > 1. A2808

The nonnegative even numbers: a(n) = 2n. A5843

Numbers that are not squarefree. Numbers that are divisible by a square greater than 1. The complement of A005117. A13929

Triangle read by rows: T(n,k) = ∑_j>=0 j!*T(n-j-1, k-1) for n >= 0, k >= 0. A84938

Moser-de Bruijn sequence: sums of distinct powers of 4. A695

The nonprime numbers: 1 together with the composite numbers, A002808. A18252

a(n) = n·2^n-1. A1787

Abundant numbers (sum of divisors of m exceeds 2m). A5101

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