One of the most widespread of superstitious beliefs is that the number 13 is unlucky. So pervasive is this notion that many hotels and office buildings in Europe and the United States do not have a room number 13.
In Scandinavian mythology there were 12 Aesir or gods living in relative harmony until the god Loki came among them, making the 13th. Loki was cruel and evil, and according to the myths, he took special delight in causing human misfortunes. Because he was evil, and because he was the 13th member of the hierarchy of the gods, the number 13 came to be looked upon as an omen of ill luck. Another explanation for the origin of this superstition also comes from Scandinavian mythology, which states the winged Valkyries, who waited to escort the heroes fallen in battle to Valhalla, were 13 in number.
The most popular explanation for the superstition surrounding the number 13 is that there were 12 apostles and their master Jesus (c. 6 B.C.E.–c. 30 C.E.) who partook of the Last Supper, Judas Iscariot being represented as the 13th guest. According to Christian tradition, Judas betrayed his master after they had observed the Passover meal. Judas later hanged himself because of his guilt, and he was said to be damned for all time as his punishment.
It has long been a matter of etiquette in France to avoid having exactly 13 guests at a dinner or party. Napoleon (1769–1821) wouldn't allow a dinner to begin if there were 13 guests at the table. There is a custom of the "quartrozieme," a professional guest who can be called on short notice to avoid having only 13 people dining at a dinner party. Although the superstition of 13 guests is not quite so strong in the United States, President Herbert Hoover (1874–1964) would not permit a gathering of 13 while he was in the White House. President Franklin D. Roosevelt (1882–1945) had the same superstition, and it is said that his personal secretary was often called upon to be the 14th guest at a dinner party.
The number seven has been regarded with superstitious awe for centuries—some consider seven to be lucky; others, unlucky. Rather than being viewed as bringing good fortune or misfortune, the number seven has long been considered a digit of great power. For example, there are seven ecstasies of Zoroaster, the seventh day that celebrates the Sabbath, the seven days of the week, the seven golden candlesticks of Solomon's temple. Among various early peoples, the seventh son of a seventh son was believed to be born with supernatural powers, a boy who would become a wizard when he grew to manhood. Likewise, the seventh daughter of a seventh daughter was believed to be born with gifts of prophecy and healing.
Chinese and Japanese people have a superstitious fear of the number four, because the word for death, shi, sounds just like the word for four. Even in the contemporary United States, cardiac deaths for Chinese and Japanese Americans spike 7 percent higher on the fourth of each month. The number four is considered so unlucky in China and Japan that many buildings don't list a fourth floor, the Chinese air force will not assign the number to any of its aircraft, and even cartoon characters that have only four fingers are deemed bad luck.
Among many Jews, even numbers are considered unlucky, even dangerous. While there are no official Christian teachings regarding any numbers being lucky or unlucky, many people believe that the number 12 has significance because of the 12 apostles. And then there is the unholy number 666, which many Christians attribute to Satan or the Antichrist.