Hypersurfaces Invariant by Pfaff Equations

We present results expressing conditions for the existence of meromorphic first integrals for Pfaff equations of arbitrary codimension, integrable or not, on complex manifolds. These results are in the same vein as previous ones by J-P. Jouanolou and E. Ghys. We also prove an enumerative result counting the number of hypersurfaces invariant by a projective holomorphic foliation with split tangent sheaf.