Fait mathématique: 1391 is the number of squares in a 10×10 grid of squares with diagonals drawn.
Culture générale: 1391 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: October 22nd is the day in 1910 that Dr. Crippen is convicted at the Old Bailey of poisoning his wife and is subsequently hanged at Pentonville Prison in London.