Step 1: Divide the number into separate digits:
66172 => 6 6 1 7 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 6 = 0
6 to 1 = 5
1 to 7 = 6
7 to 2 = 5
2 to 6 = 4
Step 3: Combine the filters to a string:
0 5 6 5 4 = 05654