Step 1: Divide the number into separate digits:
35507 => 3 5 5 0 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
3 to 5 = 2
5 to 5 = 0
5 to 0 = 5
0 to 7 = 7
7 to 3 = 4
Step 3: Combine the filters to a string:
2 0 5 7 4 = 20574