13 has been traditionally associated with poor will and misfortune (unless you're Italian in which it's good fortune). However, most people don't know the underlying truth.
The Underlying Truth
Back when all the numbers were at peace, a horrible dictator by the name of 86 rose to power and forced all the numbers into forced labor (which was much more painful for the females mind you...). The ambitious captain 13 took it upon himself to vanquish this evil overlord. He gathered a huge fighting force, including the brave number 94, the cunning number 6, and the easily confused number 19. They were his chosen few- his captains, and together they rode into battle against 86 and his men. He tried to get the infamous number 69 on his team, but 69 stupidly rejected the offer. Go figure. The battle was long, and brutal, and a great many numbers of numbers fell bravely. Including 13 himself, who was slain near the end of the battle after first killing half of 86's army, including 69 and even 86 himself The end.
So Then, What's the Big Deal?
Because 13 died a long time ago, it's technically not supposed to exist. That's why we can't see it on floors or elevators or tombstones or Them.
Special things about the number 13
If you add the numbers in 13 up you get -3970. 13 is the only number that is written as 13. 13/1=13 no other number divided by 1 equals 13. You do not have enough fingers to count to thirteen unless you are a Mutant or a Vulcan . If you count to thirteen by ones you have to say a different number 13 times. If you are to tired to count to 13 you become unable to count to thirteen. Thirteen is spelt with less than thirteen letters. 13 is also the age where breasts begin to develop, and thus when men actually start to care about women.