Step 1: Divide the number into separate digits:
47391 => 4 7 3 9 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 7 = 3
7 to 3 = 4
3 to 9 = 6
9 to 1 = 8
1 to 4 = 3
Step 3: Combine the filters to a string:
3 4 6 8 3 = 34683