number.wiki
Number

640

640 is a composite number, even, a calendar year.

Abundant Number Harshad / Niven Year

Properties

Parity
Even
Digit count
3
Digit sum
10
Digital root
1
Palindrome
No
Divisor count
16
σ(n) — sum of divisors
1,530

Primality

Prime factorization: 2 7 × 5

Divisors & multiples

All divisors (16)
1 · 2 · 4 · 5 · 8 · 10 · 16 · 20 · 32 · 40 · 64 · 80 · 128 · 160 · 320 · 640
Aliquot sum (sum of proper divisors): 890
Factor pairs (a × b = 640)
1 × 640
2 × 320
4 × 160
5 × 128
8 × 80
10 × 64
16 × 40
20 × 32
First multiples
640 · 1,280 · 1,920 · 2,560 · 3,200 · 3,840 · 4,480 · 5,120 · 5,760 · 6,400

Representations

In words
six hundred forty
Ordinal
640th
Roman numeral
DCXL
Binary
1010000000
Octal
1200
Hexadecimal
280

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 640, here are decompositions:

  • 23 + 617 = 640
  • 41 + 599 = 640
  • 47 + 593 = 640
  • 53 + 587 = 640
  • 71 + 569 = 640
  • 83 + 557 = 640
  • 131 + 509 = 640
  • 137 + 503 = 640

Showing the first eight; more decompositions exist.

Unicode codepoint
ʀ
U+0280
Lowercase letter (Ll)

UTF-8 encoding: CA 80 (2 bytes).

Lookup U+0280 on Compart ↗ Lookup on FileFormat.Info ↗
Hex color
#000280
RGB(0, 2, 128)
IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.2.128.