Step 1: Divide the number into separate digits:
22915 => 2 2 9 1 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 2 = 0
2 to 9 = 7
9 to 1 = 8
1 to 5 = 4
5 to 2 = 3
Step 3: Combine the filters to a string:
0 7 8 4 3 = 07843