Step 1: Divide the number into separate digits:
57665 => 5 7 6 6 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 7 = 2
7 to 6 = 1
6 to 6 = 0
6 to 5 = 1
5 to 5 = 0
Step 3: Combine the filters to a string:
2 1 0 1 0 = 21010