Step 1: Divide the number into separate digits:
72737 => 7 2 7 3 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 2 = 5
2 to 7 = 5
7 to 3 = 4
3 to 7 = 4
7 to 7 = 0
Step 3: Combine the filters to a string:
5 5 4 4 0 = 55440