Step 1: Divide the number into separate digits:
86009 => 8 6 0 0 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 6 = 2
6 to 0 = 6
0 to 0 = 0
0 to 9 = 9
9 to 8 = 1
Step 3: Combine the filters to a string:
2 6 0 9 1 = 26091