Step 1: Divide the number into separate digits:
20970 => 2 0 9 7 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 0 = 2
0 to 9 = 9
9 to 7 = 2
7 to 0 = 7
0 to 2 = 2
Step 3: Combine the filters to a string:
2 9 2 7 2 = 29272