code: @GwtIncompatible // com.google.common.math.DoubleUtils
    public static boolean isPowerOfTwo(double x) {
      if (x > 0.0 && isFinite(x)) {
        long significand = getSignificand(x);
        return (significand & (significand - 1)) == 0;
      }
      return false;
    }
docs: Returns {@code true} if {@code x} is exactly equal to {@code 2^k} for some finite integer
  {@code k}.