  We investigate the relationship among several numerical invariants associated
to a (free) projective hypersurface $V$: the sequence of mixed multiplicities
of its Jacobian ideal, the Hilbert polynomial of its Milnor algebra, and the
sequence of exponents when $V$ is free. As a byproduct, we obtain explicit
equations for some of the homaloidal surfaces in the projective 3-dimensional
space constructed by C. Ciliberto, F. Russo and A. Simis.
