general_fact: 351 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 351 is the smallest number so that it and the surrounding numbers are all products of 4 or more primes.
trivia: 351 is a boring number.
historical_date: December 16th is the day in 1997 that an episode of Pokémon, "Dennō Senshi Porygon", aired in Japan induces seizures in 685 Japanese children.