Step 1: Divide the number into separate digits:
12672 => 1 2 6 7 2
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
1 to 2 => 1
2 to 6 => 4
6 to 7 => 1
7 to 2 => 5
2 to 1 => 1
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
1 => C
4 => N
1 => C
5 => N
1 => C
Step 4: Combine the filters to a string:
C N C N C = CNCNC