Fatto generale: 1637 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1637 is the number of graphs with 9 vertices and 10 edges.
Trivia: 1637 is an uninteresting number.
Data storica: June 24th is the day in 1604 that Samuel de Champlain discovers the mouth of the Saint John River, site of Reversing Falls and the present day city of Saint John, New Brunswick, Canada.