Step 1: Divide the number into separate digits:
62409 => 6 2 4 0 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
6 to 2 = 4
2 to 4 = 2
4 to 0 = 4
0 to 9 = 9
9 to 6 = 3
Step 3: Combine the filters to a string:
4 2 4 9 3 = 42493