Why it is different between -2147483648 and (int)-2147483648

Question

When I run the following code under Windows7 x64, compiled with GCC of MinGW, the result seems to be underflowed:

cout<<-2147483648 ;    //Output: 2147483648

but when I assigned it to a integer variable, or just simply convert it to the int type :

cout<<(int)-2147483648 ; //Output: -2147483648 

So, what's wrong with the previous version of my code? Istn't it the type int? or what the lower bound the Integer is exactly? Many thanks.