Even little kids know that 13 is an unlucky number, and that Friday the 13th is the unluckiest day of the year, but do you know why?
Whether or not you believe in luck, fate or chance, there's a long and spooky history behind the number that everyone is afraid of.
1. The Gallows
There's an old rumor that 13's unlucky reputation stretches back to a time when we used to hang prisoners. It's said that the gallows had 13 steps, and there are 13 loops to tie a noose. Neither is true, but it did lead to the classic joke that every gallows has 13 steps - "12 up and 1 down!"
2. Science and superstition
Don't let people tell you that being afraid of Friday the 13th makes you superstitious. A British Medical Journal study from 1993 called "Is Friday the 13th Bad for Your Health" discovered there was less traffic on the 13th (lots of people choose to stay home from work) but the number of hospital visits because of accidents went up. Scary!
3. Count the letters in your name
It's said that someone born with 13 letters in their name is cursed. Maybe you're not worried, but what if we tell you that Charles Manson, Jeffrey Dahmer, Theodore Bundy and Albert De Salvo all have 13 letter names. So does Adolf Hitler, since his full name on his birth certificate is "Adolfus."
4. Say this 10 times fast
If you have a fear of the number 13 you're triskaidekaphobic, while a fear of Friday the 13th specifically is called friggatriskaidekaphobia. But there's no need to fear, because there's a treatment center in Pennsylvania that will have you cured in no time.
5. The Last Supper
Experts who have researched the number 13 say the likely cause of all our fear is the last supper, where Jesus and his 12 disciples had their final meal together. Depending on who you ask, Jesus or Judas was the unlucky 13th guest, and some biblical scholars think Jesus was even crucified on the 13th.
Click to the next page to learn which celebrity says 13 is their lucky number!