Fatto matematico: 669 is the number of unsymmetrical ways to dissect a regular 12-gon into 10 triangles.
Trivia: 669 is an unremarkable number.
Data storica: October 30th is the day in 1226 that Tran Thu Do, head of the Tran clan of Vietnam, forces Ly Hue Tong, the last emperor of the Ly dynasty, to commit suicide.