Fatto generale: 40 is the number of attempts needed before the creation of the "water displacing" substance in the spray WD-40.
Fatto matematico: 40 is a repdigit in base 3 (1111) and a Harshad number in base 10.
Trivia: 40 is the customary number of hours in a regular workweek in some Western countries.
Data storica: February 9th is the day in 1959 that the R-7 Semyorka, the first intercontinental ballistic missile, becomes operational at Plesetsk, USSR.