math_fact: 4650 is the maximum number of regions space can be divided into by 25 spheres.
trivia: 4650 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: September 23rd is the day in 1122 that Pope Calixtus II and Holy Roman Emperor Henry V agree to the Concordat of Worms to put an end to the Investiture Controversy.