Fatto generale: 1917 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1917 is the number of possible configurations of pegs (up to symmetry) after 27 jumps in solitaire.
Trivia: 1917 is an uninteresting number.
Data storica: March 31st is the day in 1964 that a coup d'état in Brazil establishes a military government, under the aegis of general Castello Branco.