Integer is power of 2

That's simple:

inline bool isPowerOf2(int i)
 {
   return i > 0 && (i & (i - 1)) == 0;
 }

Source: http://www.parashift.com/c++-faq-lite/intrinsic-types.html#faq-26.12

#include <iostream>
using namespace std;

inline bool isPowerOf2(int i)
{
    return i > 0 && (i & (i - 1)) == 0;
}

int main()
{
    cout << "64 is " << (isPowerOf2(64) ? "" : " not ") << "power of 2" << endl;
    cout << "100 is " << (isPowerOf2(100) ? "" : " not ") << "power of 2" << endl;
    cout << "128 is " << (isPowerOf2(128) ? "" : " not ") << "power of 2" << endl;
    cout << "1024 is " << (isPowerOf2(1024) ? "" : " not ") << "power of 2" << endl;
    return 0;
}