Fait général: 1664 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 1664 is a value of n so that n(n+9) is a palindrome.
Culture générale: 1664 is an unremarkable number.
Date historique: July 21st is the day in 1919 that the dirigible Wingfoot Air Express crashes into the Illinois Trust and Savings Building in Chicago, killing 12 people.