Fatto matematico: 1546 is the number of 5×5 binary matrices with at most one 1 in each row and column.
Trivia: 1546 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: March 25th is the day in 1995 that WikiWikiWeb, the world's first wiki, and part of the Portland Pattern Repository, is made public by Ward Cunningham.