math_fact: 19709 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
trivia: 19709 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: December 16th is the day in 1947 that William Shockley, John Bardeen and Walter Brattain build the first practical point-contact transistor.