Step 1: Divide the number into separate digits:
82877 => 8 2 8 7 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 2 => 6
2 to 8 => 6
8 to 7 => 1
7 to 7 => 0
7 to 8 => 1
Step 3: Convert distances to codes (0=E[qual],
1 & 9 = C[onsecutive], 2-8 = N[one]):
6 => N
6 => N
1 => C
0 => E
1 => C
Step 4: Combine the filters to a string:
N N C E C = NNCEC