Because they needed a number between 12 and 14. If 13 should not have been invented, 3 (sacred number) neither.
No, I don't think your friends will hate you if you make out under 13 but at the same time why would you need to make out under the age if 13?
13
You don't!
You don't. 13 is already prime.
13 is the unlucky
1 x 13 and 13 x 1
Yes apollo 13 did make it safely to earth with all the three astronauts.
Most children under 13 have an attempt to make one faking there age, My opinion is you to wait 'til you are 13 and check with your parents that you can make a Facebook.
Subtract 1999 from it.
338
13
No.