Step 1: Divide the number into separate digits:
18894 => 1 8 8 9 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 8 = 7
8 to 8 = 0
8 to 9 = 1
9 to 4 = 5
4 to 1 = 3
Step 3: Combine the filters to a string:
7 0 1 5 3 = 70153