math_fact: 1626 is the number of binary partitions of 31.
trivia: 1626 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: June 13th is the day in 1934 that Adolf Hitler and Benito Mussolini meet in Venice, Italy; Mussolini later describes the German dictator as "a silly little monkey".