Fatto generale: 2823 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 2823 is an unremarkable number.
Trivia: 2823 is an uninteresting number.
Data storica: September 23rd is the day in 1122 that Pope Calixtus II and Holy Roman Emperor Henry V agree to the Concordat of Worms to put an end to the Investiture Controversy.