Step 1: Divide the number into separate digits:
55080 => 5 5 0 8 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 5 => 0
5 to 0 => 5
0 to 8 => 8
8 to 0 => 8
0 to 5 => 5
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
0 => E
5 => N
8 => N
8 => N
5 => N
Step 4: Combine the filters to a string:
E N N N N = ENNNN