Fatto generale: 21913 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21913 is a boring number.
Trivia: 21913 is a boring number.
Data storica: December 29th is the day in 1876 that the Ashtabula River Railroad bridge disaster occurs, leaving 64 injured and 92 dead at Ashtabula, Ohio.