general_fact: 721 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 721 is the smallest number which can be written as the difference of 2 cubes in 2 ways.
trivia: 721 is a boring number.
historical_date: December 21st is the day in 1907 that the Chilean Army commits a massacre of at least 2,000 striking saltpeter miners in in Iquique, Chile.