Hecho general: 7923 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 7923 is a value of n for which n and 2n together use each digit 1-9 exactly once.
Trivia: 7923 is an uninteresting number.
Fecha histórica: September 9th is the day in 1970 that a British airliner is hijacked by the Popular Front for the Liberation of Palestine and flown to Dawson's Field in Jordan.