Step 1: Divide the number into separate digits:
42000 => 4 2 0 0 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 2 = 2
2 to 0 = 2
0 to 0 = 0
0 to 0 = 0
0 to 4 = 4
Step 3: Combine the filters to a string:
2 2 0 0 4 = 22004