That 11 one only works under 100.
Try this:
1. Add the digits of odd positions from left to right of the number.
2. Do the same for the even positions of the number.
3.Find the differences between them.
4. If the difference is 0 or a multiple of eleven, then the origional number is divisible by 11:
1320 1320
1+2=3 3+0=3
3-3=0
1320 is divisible by 11!
