Fatto generale: 324 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 324 is the largest possible product of positive integers with sum 16.
Trivia: 324 is an unremarkable number.
Data storica: November 19th is the day in 1095 that the Council of Clermont, called by Pope Urban II to discuss sending the First Crusade to the Holy Land, begins.