Fait général: 6663 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 6663 is a value of n for which s(n) is a repdigit.
Culture générale: 6663 is an uninteresting number.
Date historique: March 29th is the day in 1957 that the New York, Ontario and Western Railway makes its final run, the first major U.S. railroad to be abandoned in its entirety.