Fatto matematico: 917 is the only positive number known whose 9^{th} power can be written as the sum of ten 9^{th} powers.
Trivia: 917 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: July 5th is the day in 1833 that Admiral Charles Napier defeats the navy of the Portuguese usurper Dom Miguel at the third Battle of Cape St. Vincent.