Whats so important about that number? Why not 1336 or 1338..is this something to do with toribash or just randomly picked? Im interested

1337 is leet for ELITE without the first E

Use numbers that look like the letter you are using.

as omega said, 1337 is leet = elite and/or elite speak

this might help

the concept of that is to cover as many letters with numbers or symbols

I see..its very interesting

1=l
3=e
3=e
7=t
1337=leet (elite)