Hecho general: 20991 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 20991 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 20991 is an uninteresting number.
Fecha histórica: June 20th is the day in 1982 that the Argentine base (Corbeta Uruguay) on Southern Thule surrenders to Royal Marine commandos in the final action of the Falklands War.