Number

23

23 — Twenty-Three

23 is a prime, odd, a calendar year.

Twenty-three is the ninth prime, the smallest odd prime that is not a twin prime, and the answer to the birthday problem: in a group of 23 people there is roughly a 50% chance two share a birthday.

Sources https://en.wikipedia.org/wiki/23_(number)

Cousin Prime Curated Deficient Number Happy Number Prime Sexy Prime Squarefree

Properties

Parity: Odd
Digit count: 2
Digit sum: 5
Digital root: 5
Palindrome: No
Divisor count: 2
σ(n) — sum of divisors: 24

Primality

23 is prime. It has exactly two divisors: 1 and itself.

Divisors & multiples

All divisors (2)

1 · 23

Aliquot sum (sum of proper divisors): 1

Factor pairs (a × b = 23)

1 × 23

First multiples

23 · 46 · 69 · 92 · 115 · 138 · 161 · 184 · 207 · 230

Representations

In words: twenty-three
Ordinal: 23rd
Roman numeral: XXIII
Binary: 10111
Octal: 27
Hexadecimal: 17

Also seen as

Prime neighborhood

Adjacent primes:

Previous prime: 19 (gap of 4)
Next prime: 29 (gap of 6)

Pair status: cousin with 19, sexy with 29.

ASCII character

As an ASCII codepoint, 23 is control character (0x17). ASCII control character.

Network port

TCP/UDP port 23 is the well-known port for Telnet — Plaintext remote login (deprecated).

Hex color

#000017

RGB(0, 0, 23)

IPv4 address

As an unsigned 32-bit integer, this is the IPv4 address 0.0.0.23.