Step 1: Divide the number into separate digits:
29720 => 2 9 7 2 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 9 = 7
9 to 7 = 2
7 to 2 = 5
2 to 0 = 2
0 to 2 = 2
Step 3: Combine the filters to a string:
7 2 5 2 2 = 72522