Step 1: Divide the number into separate digits:
75457 => 7 5 4 5 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 5 = 2
5 to 4 = 1
4 to 5 = 1
5 to 7 = 2
7 to 7 = 0
Step 3: Combine the filters to a string:
2 1 1 2 0 = 21120