math_fact: 5773 is the index of a triangular number containing only 3 different digits.
trivia: 5773 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: October 21st is the day in 1520 that João Álvares Fagundes discovers the islands of Saint-Pierre and Miquelon, bestowing them their original name of "Islands of the 11,000 Virgins".