Fatto generale: 21986 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 21986 is an uninteresting number.
Trivia: 21986 is an uninteresting number.
Data storica: March 11th is the day in 222 that Emperor Elagabalus is assassinated, along with his mother, Julia Soaemias, by the Praetorian Guard during a revolt.