general_fact: 6668 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 6668 is the number of trees on 21 vertices with diameter 5.
trivia: 6668 is a boring number.
historical_date: April 3rd is the day in 1981 that the Osborne 1, the first successful portable computer, is unveiled at the West Coast Computer Faire in San Francisco.