Fatto generale: 867 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 867 is the number of graphs with 8 vertices that have chromatic number 5.
Trivia: 867 is a boring number.
Data storica: May 16th is the day in 1527 that the Florentines drive out the Medici for a second time and Florence re-establishes itself as a republic.