Step 1: Divide the number into separate digits:
2652 => 2 6 5 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 6 = 4
6 to 5 = 1
5 to 2 = 3
2 to 2 = 0
Step 3: Combine the filters to a string:
4 1 3 0 = 4130