Step 1: Divide the number into separate digits:
28573 => 2 8 5 7 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 8 = 6
8 to 5 = 3
5 to 7 = 2
7 to 3 = 4
3 to 2 = 1
Step 3: Combine the filters to a string:
6 3 2 4 1 = 63241