general_fact: 4923 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
math_fact: 4923 is an unremarkable number.
trivia: 4923 is a boring number.
historical_date: June 23rd is the day in 1938 that the Civil Aeronautics Act is signed into law, forming the Civil Aeronautics Authority in the United States.