March 3rd: The number three

On the third day of the third month, ten facts about the number three.

1. Pythagoras saw the number three as a noble number, because it is the only one which equals the sum of all the numbers below it (ie 1 + 2 = 3).
2. Three is the atomic number of lithium.
3. You can work out if a number is divisible by three by adding its digits together. If the sum of the digits is divisible by three, the whole number is.
4. Sometimes the digit 3 has a flat top: Ʒ, to stop people from fraudulently changing a 3 into an 8.
5. Three is an important number in several world religions: the Christian Holy Trinity; the Hindu Trimurti; the Hindu Tridevi; the Three Jewels of Buddhism; the Three Pure Ones of Taoism and the Triple Goddess of Wicca.
6. In Christianity, also, the ministry of Jesus lasted three years, Jesus rose from the dead on the third day after his death, St Peter denied Jesus three times, and The Magi gave Jesus three gifts.
7. Three is the first odd prime number and the second smallest prime.
8. Three is a lucky number in Chinese culture because the word for it sounds similar to the word for "alive".
9. It's often said that bad luck "comes in threes" especially bad things like deaths or plane crashes.
10. Other superstitions involving threes include an East and Southeast Asia one about it being bad luck to take a photo with three people in it, because the one in the middle will die first. Another superstition is that is is unlucky for three people to light a cigarette from the same lighter or match. This is said to have started in the trenches of World War I. A sniper might see the first light, take aim at the second, and fire on the third.