Fatto generale: 856 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 856 is a member of the Fibonacci-type sequence starting with 1 and 9.
Trivia: 856 is an uninteresting number.
Data storica: May 5th is the day in 1994 that the signing of the Bishkek Protocol between Armenia and Azerbaijan effectively freezes the Nagorno-Karabakh conflict.