Step 1: Divide the number into separate digits:
47815 => 4 7 8 1 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 7 = 3
7 to 8 = 1
8 to 1 = 7
1 to 5 = 4
5 to 4 = 1
Step 3: Combine the filters to a string:
3 1 7 4 1 = 31741