Step 1: Divide the number into separate digits:
27309 => 2 7 3 0 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 7 = 5
7 to 3 = 4
3 to 0 = 3
0 to 9 = 9
9 to 2 = 7
Step 3: Combine the filters to a string:
5 4 3 9 7 = 54397