Properties of the Number 640

Six Hundred Forty

Basics

Value: 639 → 640 → 641

Parity: even

Prime: No

Previous Prime: 631

Next Prime: 641

Digit Sum: 10

Digital Root: 1

Palindrome: No

Factorization: 2 ⁷ × 5

Divisors: 1, 2, 4, 5, 8, 10, 16, 20, 32, 40

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

4823 Try Today's Challenge

Representations

Binary: 1010000000

Octal: 1200

Duodecimal: 454

Hexadecimal: 280

Square: 409600

Square Root: 25.298221281347036

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

Number of rooted trees with n vertices in which vertices at the same level have the same degree. A3238

Numbers k that divide the (right) concatenation of all numbers <= k written in base 2 (most significant digit on left). A29447

a(n) = n*φ(n). A2618

Numbers of the form 2ⁱ*5^j with i, j >= 0. A3592

Y-toothpick sequence (see Comments lines for definition). A160120

Sums of two distinct powers of 2. A18900

Increasing sequence generated by these rules: a(1)=1, and if·is in a then 3x-2 and 4x-2 are in a. A191113

Sextuple factorials, 6-factorials, n!!!!!!, n!6. A85158

Number of parts in all partitions of n into distinct parts. A15723

a(n) = 5·2ⁿ. A20714