General fact: 7923 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 7923 is a value of n for which n and 2n together use each digit 1-9 exactly once.
Trivia: 7923 is a boring number.
Historical date: September 9th is the day in 2010 that a natural gas pipeline explosion in San Bruno, California, creates a "wall of fire" more than 1,000 feet (300 m) high.