Fait mathématique: 1606 is the number of strongly connected digraphs with 4 vertices.
Culture générale: 1606 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: May 24th is the day in 1988 that the fourth game of the 1988 Stanley Cup Finals between the Edmonton Oilers and the Boston Bruins had to end in a tie because of a power failure.