Let $n$ be a positive integer. Determine, in terms of $n$, the greatest integer which divides
every number of the form $p + 1$, where $p \equiv 2$ mod $3$ is a prime number which does not divide $n$.

1. **Identify the form of the prime number \( p \):**
   Given that \( p \equiv 2 \pmod{3} \), we can write:
   \[
   p = 3k + 2 \quad \text{for some integer } k.
   \]

2. **Express \( p + 1 \) in terms of \( k \):**
   Adding 1 to both sides of the equation \( p = 3k + 2 \), we get:
   \[
   p + 1 = 3k + 3 = 3(k + 1).
   \]
   This shows that \( p + 1 \) is always divisible by 3.

3. **Check divisibility by 2:**
   Since \( p \) is a prime number and \( p \equiv 2 \pmod{3} \), \( p \) must be odd (the only even prime is 2, which does not satisfy \( p \equiv 2 \pmod{3} \)). Therefore, \( p \) is odd, and \( p + 1 \) is even. Hence, \( p + 1 \) is divisible by 2.

4. **Combine the results:**
   Since \( p + 1 \) is divisible by both 2 and 3, it must be divisible by their least common multiple (LCM), which is 6. Therefore, \( p + 1 \) is divisible by 6.

5. **Greatest integer dividing every \( p + 1 \):**
   We need to determine the greatest integer that divides every number of the form \( p + 1 \) for all primes \( p \equiv 2 \pmod{3} \) that do not divide \( n \). From the above steps, we know that 6 divides every such \( p + 1 \).

6. **Verify if any larger integer can divide \( p + 1 \):**
   To check if any larger integer can divide \( p + 1 \), consider any integer \( d \) that divides \( p + 1 \) for all such primes \( p \). Since \( p + 1 \) is always divisible by 6, \( d \) must be a divisor of 6. The divisors of 6 are 1, 2, 3, and 6. The greatest of these is 6.

Therefore, the greatest integer that divides every number of the form \( p + 1 \), where \( p \equiv 2 \pmod{3} \) is a prime number that does not divide \( n \), is 6.

\[
\boxed{6}
\]