Where to store a 12-digit hash?

Question

MySQL

I want to use a random 12-digit numerically literal value as a primary key for mysql.
the question is what is better to store char, varchar, binary?

Answer 1

Of course char(12), because you have a constant size.
That's just the primary key and random value is the source of big problems.
Highly complicate the system by checking for collisions on the primary key.

Answer 2

doesn't matter absolutely. which is more convenient for the final result, in that and store