general_fact: 7231 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 7231 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
trivia: 7231 is an unremarkable number.
historical_date: October 18th is the day in 1860 that the Second Opium War finally ends at the Convention of Peking with the ratification of the Treaty of Tientsin, an unequal treaty.