Fatto generale: 21971 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21971 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 21971 is an uninteresting number.
Data storica: February 25th is the day in 1932 that Adolf Hitler obtains German citizenship by naturalization, which allows him to run in the 1932 election for Reichspräsident.