Fatto generale: 21981 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21981 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 21981 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: March 6th is the day in 1946 that Ho Chi Minh signs an agreement with France which recognizes Vietnam as an autonomous state in the Indochinese Federation and the French Union.