The following are excerpts from articles I found on the internet about the number 13. How many positive things can you think of that are associated with the number 13 (i.e., baker's dozen, 13 original American colonies, etc.) UNLUCKY 13 Herald-Tribune The best known unlucky number is 13. Some historians claim two U.S. presidents, Herbert Hoover and Franklin D. Roosevelt, never allowed 13 people to share a meal. If true, both men suffered from triskaidekaphobia or fear of the number 13, and they arent alone. The Stress Management Center and Phobia Institute in Asheville, N.C., estimates American businesses lose more than $800 million each Friday the 13th because some people will not travel to go to work. Different nations have different unlucky numbers and days. If you lived in a Spanish-speaking country, Tuesday the 13th or any Tuesday would be an unlucky day. A Spanish proverb says en martes, ni te cases ni te embarques (On Tuesday, neither get married nor start a journey.) The Japanese do not like the numbers four and nine because they pronounce four as shi, which is the same pronunciation as the word for death. Nine is pronounced ku, which has the same pronunciation as the word for agony. Many Japanese hospitals do not use four or nine as room numbers, and weve heard there are no seats numbered four or nine on any All Nippon Airways airlines. The number four is so unlucky in China that the cartoon the Simpsons was originally unpopular because Bart has only four fingers on each hand. Friday the 13th By Jon Bowen for slate.com engineers and architects go to great lengths to soothe our superstition. Skyscrapers and hotels have no 13th floor; airplanes have no 13th aisle. But the joke is on triskaidekaphobics, of course, since the 13th aisle is sitting right there behind the 12th, obviously -- it's just labeled as 14 to hoodwink you into relaxing. So where does the fear of 13 come from? Its origins can be traced to Norse mythology and a dinner party at Valhalla, home of the god Odin, where Odin and 11 of his closest god-friends were gathered one night to party. Everyone was having fun, but then Loki, the dastardly god of evil and turmoil, showed up uninvited, making it a crowd of 13. The legend goes that the beloved god Balder tried to boot Loki out of the house, and in the scuffle that followed he suffered a deathblow. From that mythological start, the number 13 has plowed a path of devastation through history. There were 13 people at Christ's Last Supper, including the double-crossing Judas Iscariot. The ill-fated Apollo 13 lunar mission left the launching pad at 13:13 hours and was aborted on April 13. Friday hasn't been much kinder to us. Friday was execution day in ancient Rome -- Jesus was crucified on a Friday. Put it all together, and Friday the 13th spells trouble for triskaidekaphobics. It's a testament to the phobia's prevalence that Hollywood was able to parlay our fear into a hugely successful series of slasher movies starring a hockey-masked guy named Jason. But triskaidekaphobia isn't an exclusively American affliction. Italians omit the number 13 from their national lottery. There is a hush-hush organization in France whose exclusive purpose is to provide last-minute guests for dinner parties, so that no party host ever has to suffer the curse of entertaining 13 guests.