Fatto generale: 15978 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Fatto matematico: 15978 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Trivia: 15978 is an unremarkable number.
Data storica: September 29th is the day in 2004 that the Burt Rutan Ansari X Prize entry SpaceShipOne performs a successful spaceflight, the first of two required to win the prize.