Fait mathématique: 1617 is the maximum value of n so that there exist 6 denominations of stamps so that every postage from 1 to n can be paid for with at most 9 stamps.
Culture générale: 1617 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: June 4th is the day in 2001 that Gyanendra, the last King of Nepal, ascends to the throne after the massacre in the Royal Palace.