Fait général: 2828 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 2828 is a value of n so that n(n+8) is a palindrome.
Culture générale: 2828 is an uninteresting number.
Date historique: September 28th is the day in 1958 that France ratifies a new Constitution of France; the French Fifth Republic is then formed upon the formal adoption of the new constitution on October 4.