BIGINT[(M)] [UNSIGNED] [ZEROFILL]

A large integer. The signed range is -9223372036854775808 to
9223372036854775807. The unsigned range is 0 to 18446744073709551615.

SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.

URL: http://dev.mysql.com/doc/refman/5.1/en/numeric-type-overview.html

