Step 1: Divide the number into separate digits:
55905 => 5 5 9 0 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 5 = 0
5 to 9 = 4
9 to 0 = 9
0 to 5 = 5
5 to 5 = 0
Step 3: Combine the filters to a string:
0 4 9 5 0 = 04950