Fatto generale: 23561 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 23561 is an unremarkable number.
Trivia: 23561 is a boring number.
Data storica: July 3rd is the day in 1886 that the New York Tribune becomes the first newspaper to use a linotype machine, eliminating typesetting by hand.