Do you have Triskaidekaphobia? If you have this phobia, you may be a bit nervous to leave home today. Triskaidekaphobia is the "fear of the number 13." Americans lose millions of dollars every year because of this phobia. People cancel train tickets, plane tickets, and much more on the 13th of every month. Many hotels and buildings don't even have a 13th floor. Some believe that the number 13 is considered bad luck because 13 people sat at The Last Super the night Judas betrayed Jesus. Even Napoleon, Hebert Hoove,r and Franklin D. Roosevelt would not sit at dinner parties if there were 13 people.