231 is a Triangular Number.
231 is a Hexagonal Number.
231 is an Octahedral Number.
231 is a 17-gonal Number.
231 is a 78-gonal Number.
231 is a Centered 23-gonal Number.
The 231 two-letter combinations of the 22 letters of the Hebrew Alphabet referred to as the 231 gates of Sefer Yetzirah.
Two hundred thirty-one is the exact number of cubic inches in a U.S. liquid gallon.
The Year 231 AD
In the year 231 AD Origen, disciple of Ammonius Saccas, founder of Neoplatonism , was exiled in Caesarea.