Some more facts about the number 40:
1. Forty is the only number in English which has its letters in alphabetical order.
2. Minus 40 degrees, or “40 below”, is the only temperature that is the same in both Fahrenheit and Celsius.
3. When the bubonic plague gripped Europe during the Middle Ages, ships would be isolated in harbours for 40 days before passengers could go ashore. The word quarantine originates from the Venetian dialect form of the Italian quaranta giorni, meaning “40 days”.
4. There are 40 spaces on a Monopoly board. Proving that life is a gamble, the game gives players equal chances (one in 40) of going directly to jail or winning the Free Parking prize.
5. Forget “nine months” – a typical pregnancy actually lasts 40 weeks.
6. In literature, 40 is the number of thieves Ali Baba clashes with in the “Arabian Nights” tale.
7. Also, 40 is the number of winks Dr William Kitchiner suggests taking for a perfect nap in his 1821 guide, hence the expression 'forty winks' for nap
Source: Google