In some countries, the number thirteen does not exist in addresses. The address 12 is often followed by number 12 1/2 ,and then by 14. Many buildings in the united states do not have a floor labeled 13,and the buttons on elevators skip the number thirteen. Some people will not buy or use anything that has the number thirteen on it. Historians guess that the origin of number thirteen's unlucky reputation could be based on the bible. Thirteen represents the number of people present at the last supper before christ was put to death.