Step 1: Divide the number into separate digits:
19215 => 1 9 2 1 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 9 = 8
9 to 2 = 7
2 to 1 = 1
1 to 5 = 4
5 to 1 = 4
Step 3: Combine the filters to a string:
8 7 1 4 4 = 87144