Fait mathématique: 7884 is a value of n for which 2n and 5n together use each digit exactly once.
Culture générale: 7884 is a boring number.
Date historique: August 1st is the day in 1203 that Isaac II Angelus, restored Eastern Roman Emperor, declares his son Alexius IV Angelus co-emperor after pressure from the forces of the Fourth Crusade.