Fatto generale: 823 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 823 is a number that does not have any digits in common with its cube.
Trivia: 823 is an uninteresting number.
Data storica: April 2nd is the day in 2002 that Israeli forces surround the Church of the Nativity in Bethlehem into which armed Palestinians had retreated.