General fact: 1539 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 1539 is an unremarkable number.
Trivia: 1539 is a boring number.
Historical date: March 18th is the day in 1992 that White South Africans vote overwhelmingly in favour, in a national referendum, to end the racist policy of Apartheid.