Curved spacetime embedded in noncurved spacetime

Let us say, that we have a curved spacetime, for instance, Schwarzschild metric. Can it be embedded in five dimensional noncurved Lorentzian spacetime, or we need six dimensional Lorentzian spacetime with two time dimensions?

Books only write that it is not necessary that this space is embedded in more dimensional spacetime, but it is not written, how it is when it IS embedded.