How big can a 64bit signed integer be?

This article is good for more information about this topic: http://en.wikipedia.org/wiki/Integer_(computer_science)

So the answer to the question should be: From -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807, or from −(2^63) to 2^63 − 1

The highest positive number stored in a signed int is represented binary as

----- 63 ones -----

0111111111111111111111111111111111111111111111111111111111111111

If you think carefully you can find out that this number is exactly 2^63 - 1.

A signed integer ranges from size −2^(n−1) through 2^(n−1) − 1 so in this case the maximum value would be 2 ^ 63 - 1 or 9,223,372,036,854,775,807