general_fact: 2015 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 2015 is a Lucas-Carmichael number.
trivia: 2015 is a boring number.
historical_date: July 7th is the day in 2002 that a scandal breaks out in the United Kingdom when news reports accuse MI6 of sheltering Abu Qatada, the supposed European Al Qaeda leader.