The number considered unlucky in many cultures is the number 13. This superstition, known as triskaidekaphobia, is prevalent in Western societies, where various traditions and beliefs suggest that the number 13 brings bad luck. Many buildings skip the 13th floor, going directly from 12 to 14, and some calendars omit the 13th day in certain contexts. The origin of this belief may be traced to various historical and cultural stories, including the Last Supper, where Judas Iscariot, the betrayer of Jesus, is thought to have been the 13th guest at the table.