Fait mathématique: 4650 is the maximum number of regions space can be divided into by 25 spheres.
Culture générale: 4650 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: September 23rd is the day in 1641 that the Merchant Royal, carrying a treasure worth over a billion US dollars, is lost at sea off Land's End.