Fatto generale: 91211 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 91211 is an uninteresting number.
Trivia: 91211 is a boring number.
Data storica: September 22nd is the day in 1236 that the Lithuanians and Semigallians defeat the Livonian Brothers of the Sword in the Battle of Saule.