Hecho general: 687 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 687 is the closest integer to 8^{p}.
Trivia: 687 is an unremarkable number.
Fecha histórica: November 17th is the day in 1973 that the Athens Polytechnic Uprising against the military regime ends in a bloodshed in the Greek capital.