math_fact: 6276 is a value of n for which f(n) = f(reverse(n)).
trivia: 6276 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: March 7th is the day in 321 that Emperor Constantine I decrees that the dies Solis Invicti (sun-day) is the day of rest in the Empire.