number.wiki
Number

4

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

Deficient Number Harshad / Niven Lucas Narcissistic / Armstrong Perfect Square Power of Two Powerful Number Smith Number Tetrahedral Year

Properties

Parity
Even
Digit count
1
Digit sum
4
Digital root
4
Palindrome
Yes
Divisor count
3
σ(n) — sum of divisors
7

Primality

Prime factorization: 2 2

Divisors & multiples

All divisors (3)
1 · 2 · 4
Aliquot sum (sum of proper divisors): 3
Factor pairs (a × b = 4)
1 × 4
2 × 2
First multiples
4 · 8 · 12 · 16 · 20 · 24 · 28 · 32 · 36 · 40

Representations

In words
four
Ordinal
4th
Roman numeral
IV
Binary
100
Octal
4
Hexadecimal
4

Also seen as

Goldbach decomposition

Goldbach's conjecture says every even integer greater than 2 is the sum of two primes. For 4, here are decompositions:

  • 2 + 2 = 4
ASCII character

As an ASCII codepoint, 4 is control character (0x04). ASCII control character.

Hex color
#000004
RGB(0, 0, 4)
IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.4.