Step 1: Divide the number into separate digits:
37391 => 3 7 3 9 1
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 7 = 4
7 to 3 = 4
3 to 9 = 6
9 to 1 = 8
1 to 3 = 2
Step 3: Combine the filters to a string:
4 4 6 8 2 = 44682