Step 1: Divide the number into separate digits:
72509 => 7 2 5 0 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 2 = 5
2 to 5 = 3
5 to 0 = 5
0 to 9 = 9
9 to 7 = 2
Step 3: Combine the filters to a string:
5 3 5 9 2 = 53592