General fact: 17561 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 17561 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 17561 is a boring number.
Historical date: January 29th is the day in 904 that Sergius III comes out of retirement to take over the papacy from the deposed antipope Christopher.