Very strange behaviour in primary key field!!

I have a table with a primary key field (Code) type (int(11)), value insert manually.
When i insert this value: 30201010 it goes well and saved without any problem, When i insert 3020101010 the data saved but the number in the primary key field changed to 2147483647 !!!
So 3020101010 will be 2147483647 after record save :wink:

Please help …

Because its the max positive number for a signed int.
http://en.m.wikipedia.org/wiki/Integer_(computer_science)

Thanks so much (Giu). Appreciate your help.