Step 1: Divide the number into separate digits:
72440 => 7 2 4 4 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 2 = 5
2 to 4 = 2
4 to 4 = 0
4 to 0 = 4
0 to 7 = 7
Step 3: Combine the filters to a string:
5 2 0 4 7 = 52047