Step 1: Divide the number into separate digits:
49802 => 4 9 8 0 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
4 to 9 = 5
9 to 8 = 1
8 to 0 = 8
0 to 2 = 2
2 to 4 = 2
Step 3: Combine the filters to a string:
5 1 8 2 2 = 51822