General fact: 7894 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 7894 is a value of n for which n and 8n together use each digit 1-9 exactly once.
Trivia: 7894 is an unremarkable number.
Historical date: August 11th is the day in 3114 BC that the Mesoamerican Long Count calendar, used by several pre-Columbian Mesoamerican civilizations, notably the Mayans, begins.