Fatto generale: 1861 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1861 is an uninteresting number.
Trivia: 1861 is an unremarkable number.
Data storica: February 3rd is the day in 1966 that the unmanned Soviet Luna 9 spacecraft makes the first controlled rocket-assisted landing on the Moon.