Step 1: Divide the number into separate digits:
9642 => 9 6 4 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
9 to 6 = 3
6 to 4 = 2
4 to 2 = 2
2 to 9 = 7
Step 3: Combine the filters to a string:
3 2 2 7 = 3227