Step 1: Divide the number into separate digits:
00237 => 0 0 2 3 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 0 => 0
0 to 2 => 2
2 to 3 => 1
3 to 7 => 4
7 to 0 => 7
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
0 => E
2 => N
1 => C
4 => N
7 => N
Step 4: Combine the filters to a string:
E N C N N = ENCNN