General fact: 7473 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Mathematical fact: 7473 is a Tribonacci-like number starting from 1, 1, and 1.
Trivia: 7473 is a boring number.
Historical date: June 16th is the day in 1972 that the largest single-site hydro-electric power project in Canada is inaugurated at Churchill Falls, Labrador.