Fait mathématique: 21780 is an uninteresting number.
Culture générale: 21780 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Date historique: August 18th is the day in 1977 that Steve Biko is arrested at a police roadblock under the Terrorism Act No 83 of 1967 in King William's Town, South Africa.