general_fact: 15643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 15643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
trivia: 15643 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
historical_date: October 29th is the day in 2008 that Delta Air Lines merges with Northwest Airlines, creating the world's largest airline and reducing the number of US legacy carriers to 5.