Hecho matemático: 6729 is the smallest value of n for which n and 2n together use each digit 1-9 exactly once.
Trivia: 6729 is a boring number.
Fecha histórica: June 3rd is the day in 1973 that a Soviet supersonic Tupolev Tu-144 crashes near Goussainville, France, killing 14, the first crash of a supersonic passenger aircraft.