233 is an interesting Fibonacci prime. If divided by the Fibonacci number 144, it approximates the golden ratio.
2233 - 3 is prime. [Kulsha]
Describing 233 and repeating the process with each new term produces five more primes, i.e., "one 2, two 3's," generates 1223, etc. [Rivera]
The only known Fibonacci prime whose sum of digits is a Fibonacci number. [Russo]
Had Ray Bradbury used the metric system, he may have called his novel "Celsius 233." [Hartley]
Claimed to be the first book with no verbs, The Train from Nowhere by Michel Thaler (a pseudonym) has 233 pages. [Opao]
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.
233+(2+3+3), 233+2*3*3, and 233+2^3*3 are consecutive primes. [Silva]
The smallest magic constant of a 5-by-5 prime magic square:
41 11 79 19 83 31 67 29 89 17 61 59 05 71 37 97 53 13 47 23 03 43 107 07 73Note that this solution includes all the twenty-four odd primes below hundred (Andrew Lelechenko, 2009). [Beedassy]
Jewel Cave in South Dakota contains 233 kilometers of mapped passageways. [Robinette]
The largest known Fibonacci prime with exactly two different digits. Note the first two primes. [Capelle]
"The triangular theorem of eight and non-finiteness results for quadratic polynomials" by Wieb Bosma and Ben Kane conjectures that the largest of all values in a sequence related to Universal Quadratic Forms, the representability of integers as sums of triangular numbers, and the 290-Theorem, is 233. [Post]
The larger of only two primes less than a googol formed by concatenating a number n followed by n 3's. The other is 13. [Loungrides]
The only multidigit prime-digit Fibonacci prime. [Loungrides]
233: (233, 239, 241, 251, 257) is the only case of five consecutive 3-digit primes p < q < r < s < t, such that p divides q*r*s*t+1. Note that the sequence of primes 2, 3, 5, 7, 11 is the previous case with the same property. [Loungrides]
A potentially rocky planet, known as Barnard's star b, is a 'super-Earth' that orbits around its host star once every 233 days.
(There are 4 curios for this number that have not yet been approved by an editor.)