233 (number)

233 is the natural number between 232 and 234. It is also a prime number.

← 200 210 220 230 240 250 260 270 280 290 → List of numbers — Integers ← 0 100 200 300 400 500 600 700 800 900 →
Ordinal	Two hundred [and] thirty-three
Cardinal	233rd Two hundred and thirty-third
Factorization	prime number
Roman numeral	CCXXXIII
Binary	11101001
Hexadecimal	E9

In mathematics

233 is an irregular prime, a full reptend prime, a cousin prime, a Chen prime, a Fibonacci prime and a sexy prime. It is the 13th Fibonacci number. It is an Eisenstein prime of the form $3n - 1$ with no imaginary part. Since 233 × 2 + 1 = 467, another prime, 233 is a Sophie Germain prime. 233 is also a prime triplet (with 227 and 229).

It is the 13th Fibonacci number, being the sum of 89 and 144. Being an odd-indexed Fibonacci number, it is also a Markov number, appearing in solutions to the Markov Diophantine equation: (1, 89, 233), (89, 233, 610), (233, 610, 426389), ...

In base 10 there is no integer that added up to its own digits yields 233, hence 233 is a self number. In base 3, the sum of 233's digits is composite; no smaller prime has this property.

In other fields

In current teenage slang and Internet discourse, 233 is sometimes used instead of BFF to abbreviate "Best Friends Forever." The digits correspond to the number keys that would be pressed on a telephone while sending a text message. In Windows live messenger 233 is a commonly used to represent the emoticon of raised eybrows.

Chinese twitter users like use 233 to express the Internet abbr LOL, it comes from the 233rd emotion icon on popular Chinese website mop.com, the GIF shows an LOL animation, picture link.

In literature

233 is the final chapter of The Curious Incident of the Dog in the Night-Time by Mark Haddon, which uses all prime numbers for its chapters due to its narrator's Asperger's syndrome.