Step 1: Divide the number into separate digits:
28613 => 2 8 6 1 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 8 = 6
8 to 6 = 2
6 to 1 = 5
1 to 3 = 2
3 to 2 = 1
Step 3: Combine the filters to a string:
6 2 5 2 1 = 62521