general_fact: 15 is the length in miles of a train of boxcars that can be filled from recycled paper in the USA every day.
math_fact: 15 is the smallest number that can be factorized using Shor's quantum algorithm.
trivia: 15 is the number of times an average person laughs a day.
historical_date: January 15th is the day in 1993 that Salvatore Riina, the Mafia boss known as "The Beast", is arrested in Sicily, Italy after three decades as a fugitive.