Step 1: Divide the number into separate digits:
38513 => 3 8 5 1 3
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 8 = 5
8 to 5 = 3
5 to 1 = 4
1 to 3 = 2
3 to 3 = 0
Step 3: Combine the filters to a string:
5 3 4 2 0 = 53420