Fatto generale: 23 is the number of enigma that plays a prominent role in the plot of The Illuminatus! Trilogy by Robert Shea and Robert Anton Wilson.
Fatto matematico: 23 is the first prime P for which unique factorization of cyclotomic integers based on the Pth root of unity breaks down.
Trivia: 23 is the number of times Julius Caesar was stabbed.
Data storica: January 23rd is the day in 1855 that the first bridge over the Mississippi River opens in what is now Minneapolis, Minnesota, a crossing made today by the Father Louis Hennepin Bridge.