general_fact: 660 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 660 is the order of a non-cyclic simple group.
trivia: 660 is an uninteresting number.
historical_date: October 21st is the day in 1973 that John Paul Getty III's ear is cut off by his kidnappers and sent to a newspaper in Rome; it doesn't arrive until November 8.