Fait mathématique: 6663 is a value of n for which s(n) is a repdigit.
Culture générale: 6663 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: March 29th is the day in 1961 that the Twenty-third Amendment to the United States Constitution is ratified, allowing residents of Washington, D.C., to vote in presidential elections.