13 facts about Friday the 13th, the first of 3 this year

If you fear Friday the 13th, then batten down the hatches. This week's unlucky day is the first of three this year.

The next Friday the 13th comes in March, followed by Nov. 13. Such a triple whammy comes around only every 11 years, said Thomas Fernsler, a math specialist at the University of Delaware who has studied the number 13 for more than 20 years.

Here are 13 more facts about the infamous day, courtesy of Fernsler and some of our own research:

1. The British Navy built a ship named Friday the 13th. On its maiden voyage, the vessel left dock on a Friday the 13th, and was never heard from again.

2. The ill-fated Apollo 13 launched at 13:13 CST on Apr. 11, 1970. The sum of the date's digits (4-11-70) is 13 (as in 4+1+1+7+0 = 13). And the explosion that crippled the spacecraft occurred on April 13 (not a Friday). The crew did make it back to Earth safely, however.

3. Many hospitals have no room 13, while some tall buildings skip the 13th floor.

4. Fear of Friday the 13th - one of the most popular myths in science - is called paraskavedekatriaphobia as well as friggatriskaidekaphobia. Triskaidekaphobia is fear of the number 13.

5. Quarterback Dan Marino wore No. 13 throughout his career with the Miami Dolphins. Despite being a superb quarterback (some call him one of the best ever), he got to the Super Bowl just once, in 1985, and was trounced 38-16 by the San Francisco 49ers and Joe Montana (who wore No. 16 and won all four Super Bowls he played in).

6. Butch Cassidy, notorious American train and bank robber, was born on Friday, April 13, 1866.

7. Fidel Castro was born on Friday, Aug. 13, 1926.

8. President Franklin D. Roosevelt would not travel on the 13th day of any month and would never host 13 guests at a meal. Napoleon and Herbert Hoover were also triskaidekaphobic, with an abnormal fear of the number 13.

9. Superstitious diners in Paris can hire a quatorzieme, or professional 14th guest.

10. Mark Twain once was the 13th guest at a dinner party. A friend warned him not to go. "It was bad luck," Twain later told the friend. "They only had food for 12."

11. Woodrow Wilson considered 13 his lucky number, though his experience didn't support such faith. He arrived in Normandy, France on Friday, Dec. 13, 1918, for peace talks, only to return with a treaty he couldn't get Congress to sign. (The ship's crew wanted to dock the next day due to superstitions, Fernsler said.) He toured the United States to rally support for the treaty, and while traveling, suffered a near-fatal stroke.

12. The number 13 suffers from its position after 12, according to numerologists who consider the latter to be a complete number - 12 months in a year, 12 signs of the zodiac, 12 gods of Olympus, 12 labors of Hercules, 12 tribes of Israel, 12 apostles of Jesus, 12 days of Christmas and 12 eggs in a dozen.

13. The seals on the back of a dollar bill include 13 steps on the pyramid, 13 stars above the eagle's head, 13 war arrows in the eagle's claw and 13 leaves on the olive branch. So far there's been no evidence tying these long-ago design decisions to the present economic situation.