Step 1: Divide the number into separate digits:
73985 => 7 3 9 8 5
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
7 to 3 = 4
3 to 9 = 6
9 to 8 = 1
8 to 5 = 3
5 to 7 = 2
Step 3: Combine the filters to a string:
4 6 1 3 2 = 46132