depends on the primary key filed and how it is set up.
the maximum value for the smallint data type column is 32767 if signed (+/-) or 65535 if unsigned.
i recommend using the int data type unsigned, and make sure to set the length to 11, this allows for a max of 4294967295
http://dev.mysql.com/doc/refman/5.0/en/integer-types.html