Fatto matematico: 5574 is the number of trees on 31 vertices with diameter 4.
Trivia: 5574 is an unremarkable number.
Data storica: April 5th is the day in 1609 that Daimyo (Lord) of the Satsuma Domain in southern Kyūshū, Japan, completes his successful invasion of the Ryūkyū Kingdom in Okinawa.