general_fact: 1351 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 1351 is an uninteresting number.
trivia: 1351 is an unremarkable number.
historical_date: September 12th is the day in 1933 that Leó Szilárd, waiting for a red light on Southampton Row in Bloomsbury, conceives the idea of the nuclear chain reaction.