Step 1: Divide the number into separate digits:
6179 => 6 1 7 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 1 = 5
1 to 7 = 6
7 to 9 = 2
9 to 6 = 3
Step 3: Combine the filters to a string:
5 6 2 3 = 5623