Fait général: 6745 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fait mathématique: 6745 is the maximum value of n so that there exist 4 denominations of stamps so that every postage from 1 to n can be paid for with at most 25 stamps.
Culture générale: 6745 is an unremarkable number.
Date historique: June 19th is the day in 1179 that the Norwegian Battle of Kalvskinnet outside Nidaros.