Step 1: Divide the number into separate digits:
04169 => 0 4 1 6 9
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 4 => 4
4 to 1 => 3
1 to 6 => 5
6 to 9 => 3
9 to 0 => 9
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
4 => N
3 => N
5 => N
3 => N
9 => C
Step 4: Combine the filters to a string:
N N N N C = NNNNC