Step 1: Divide the number into separate digits:
75602 => 7 5 6 0 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 5 = 2
5 to 6 = 1
6 to 0 = 6
0 to 2 = 2
2 to 7 = 5
Step 3: Combine the filters to a string:
2 1 6 2 5 = 21625