Fatto matematico: 8404 is the number of connected graphs with 9 vertices and 13 edges.
Trivia: 8404 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Data storica: January 3rd is the day in 1996 that the Motorola StarTAC, the first flip phone and one of the first mobile phones to gain widespread consumer adoption, goes on sale.