+ 233 is an interesting Fibonacci prime. If divided by the Fibonacci number 144, it approximates the golden ratio. + The smallest prime factor of 229 - 1. + 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] + Neil J. A. Sloane, editor-in-chief of the On-Line Encyclopedia of Integer Sequences, works at AT&T Shannon Laboratories in room C233. + The only known multidigit Fibonacci prime whose digits are all Fibonacci primes. [Gupta] + The only known Fibonacci prime whose sum of digits is a Fibonacci number. [Russo] + "Pascal's Wager" appears in Pensées 233. + 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]
Uranium-235 is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238 it is fissile, i.e. it can sustain fission chain reaction. It is the only fissile isotope that is a primordial nuclide or found in significant quantity in nature.