Step 1: Divide the number into separate digits:
13089 => 1 3 0 8 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 3 = 2
3 to 0 = 3
0 to 8 = 8
8 to 9 = 1
9 to 1 = 8
Step 3: Combine the filters to a string:
2 3 8 1 8 = 23818