Fatto generale: 15851 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 15851 is an uninteresting number.
Trivia: 15851 is a boring number.
Data storica: May 25th is the day in 1521 that the Diet of Worms ends when Charles V, Holy Roman Emperor, issues the Edict of Worms, declaring Martin Luther an outlaw.