How to check if a number is a power of 2

Question

Today I needed a simple algorithm for checking if a number is a power of 2.

The algorithm needs to be:

1. Simple
2. Correct for any ulong

Answer 1

private static bool IsPowerOfTwo(ulong x)
{
    var l = Math.Log(x, 2);
    return (l == Math.Floor(l));
}