math_fact: 878 is the number of 3×3 sliding puzzle positions that require exactly 29 moves to solve starting with the hole on a side.
trivia: 878 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: May 27th is the day in 1986 that the game credited as setting the template for role-playing video games, Dragon Quest is released in Japan.