A number is divisible by 11 if the difference between the sum of the digits in the odd positions counting from the left (the first, the third ...) and the sum of the remaining digits is divisible by 11.

For example:

1.58564

The sum of the digits in the odd positions counting from the left is 5+5+4=14

The sum of the remaining digits is 8+6=14

14-14=0, and 0 is divisible by 11, so 58564 is divisible by 11 too.

2.635047

The sum of the digits in the odd positions counting from the left is 6+5+4=15

The sum of the remaining digits is 3+0+7=10

15-10=5, 5 isn't divisible by 11, so 635047 isn't divisible by 11.