Fatto matematico: 873 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 873 is an unremarkable number.
Data storica: May 22nd is the day in 1816 that a mob in Littleport, Cambridgeshire, England, riots over high unemployment and rising grain costs; the rioting spreads to Ely the next day.