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!

6. Birthday luck

A handful of celebrities have been born on a Friday the 13th, including Julia Louis-Dreyfus and the Olsen twins, so it's not all bad. Singer Taylor Swift even claims 13 is her lucky number

The pop star was born on the 13th, turned 13 years old on the 13th, her first album went gold in 13 weeks, and her first #1 song had a 13 second intro. She even says that every time she wins an award she's in seat, row or section 13. Once she was even in row M - the 13th number.

7. How's this for bad luck?

Whether you believe in the superstition or not, some very freaky things have happened on Friday the 13th:

• Daz Pearson from New York died in 1976 after his roof collapsed on him (he had stayed home from work that day because it was the 13th)
• The plane crash that inspired the movie Alive, Uruguayan Air Force Flight 571, happened on Friday the 13th 1972.
• The Black Friday stock market crash of 1989
• In 2012 the Costa Concordia Cruise ship sank, killing 32 people on Friday the 13th
• A 13-year-old boy from Suffolk, England managed to survive a lightning strike on Friday, August 13th, 2010 at 1:13pm (that's 13:13 on a 24-hour clock).

8. It's not universal

Only the English-speaking world seems to fear Friday the 13th. In Italy 13 is actually lucky, and Italians say fare tredici ("to do 13") when somebody hits the jackpot. In Spanish-speaking countries, Tuesday the 13th is unlucky instead. Even the classic horror movie Friday the 13th is called Tuesday the 13th overseas.

9. You can't avoid it

Friday the 13th always happens at least once every year, but sometimes there are even more. There were 3 unlucky days in 2009 and 2012 and 2 in 2017. How can you tell when a month will have a Friday the 13th? Simple: they always start on a Sunday.

Click to the next page to find out why Superbowl 13 is called "Black Sunday!"

10. The mystery of the 13th floor

You've probably noticed an elevator or a stairwell that jumps from floor 12 or 14 before. Architects and hotel chains often do this to avoid making any visitors uncomfortable about visiting the 13th floor. According to the Otis elevator company, 85 percent of their panels "skip" the 13th floor. Some towns and cities will even avoid naming a street 13th, because who would want to live there?

11. The 13 Club

Captain William Fowler was a New Yorker who didn't have much respect for tradition or superstition. To break the taboo about the number 13, he founded the 13 Club, where he and 12 guests would sit down to a 13-course meal in a room lit by 13 candles. The club was a big hit, and over the years his guests included 5 US presidents: Chester Arthur, Grover Cleveland, Benjamin Harrison, William McKinley and Theodore Roosevelt.

12. The Knights Templar

Another popular explanation for why we're so afraid of 13 involves the Knights Templar. The Knights were guardians of religious artifacts and a sort of bank for European royalty. When the king of France found himself in debt to them, he joined forced with the pope to wipe out the order and their members. The beginning of the purge was October 13,1307.

13. Superbowl XIII

The 1979 Superbowl is still called Black Friday for its bad luck, but not by sports fans. The reigning champions the Dallas Cowboys were facing the Pittsburgh Steelers, who won in a dramatic upset. Not only did they pull out an unexpected win, they won by exactly enough points to guarantee nearly every fan who bet for them would get paid based off the Vegas odds. It was a huge single-day loss for casinos and betting parlors.

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