Step 1: Divide the number into separate digits:
40067 => 4 0 0 6 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 0 = 4
0 to 0 = 0
0 to 6 = 6
6 to 7 = 1
7 to 4 = 3
Step 3: Combine the filters to a string:
4 0 6 1 3 = 40613