The disproportionate fear of the number 13 – the seventh prime number – is called triscaidecaphobia . The term comes from the terms of Greek origin triscaideca , which means "13", and phobos , which means "fear". This superstitious belief is so ingrained that in many skyscrapers in the world the elevator jumps from the 12th to the 14th floor, and in many hotels and hospitals there are no rooms with the number 13. According to researcher Donald Dossey, in France there was a group of nobles called the quatorziennes (the "fourteen") who attended social events as the fourteenth guest when he canceled his attendance by some guest and only 13 people attended the celebration.
The specific fear of Friday the 13th is called friggatriscaidecaphobia . Another irrational phobia related to numbers is trihexaphobia , caused by the number 666.
