general_fact: 541 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 541 is the number of orderings of 5 objects with ties allowed.
trivia: 541 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: June 24th is the day in 1497 that John Cabot lands in North America at Newfoundland leading the first European exploration of the region since the Vikings.