Fatto generale: 1842 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 1842 is the number of rooted trees with 11 vertices.
Trivia: 1842 is a boring number.
Data storica: January 15th is the day in 1782 that Superintendent of Finance Robert Morris goes before the U.S. Congress to recommend establishment of a national mint and decimal coinage.