Step 1: Divide the number into separate digits:
39670 => 3 9 6 7 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 9 = 6
9 to 6 = 3
6 to 7 = 1
7 to 0 = 7
0 to 3 = 3
Step 3: Combine the filters to a string:
6 3 1 7 3 = 63173