Fait mathématique: 1637 is the number of graphs with 9 vertices and 10 edges.
Culture générale: 1637 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: June 24th is the day in 2010 that John Isner of the United States defeats Nicolas Mahut of France at Wimbledon, in the longest match in professional tennis history.