  (Abridged) We performed a multiwavelength analysis of a sample of starburst
galaxies that show the presence of a substantial population of very young
massive (WR) stars. Here we present the global analysis of the derived
photometric and chemical properties. We compare optical/NIR colours and the
physical properties (reddening coefficient, equivalent widths of the emission
and underlying absorption lines, ionization degree, electron density, and
electron temperature) and chemical properties with previous observations and
galaxy evolution models. Attending to their absolute B-magnitude many of them
are not dwarf galaxies, but they should be during their quiescent phase. We
found that both C(Hb) and Wabs increase with increasing metallicity. We
detected a high N/O ratio in objects showing strong WR features. The ejecta of
the WR stars may be the origin of the N enrichment in these galaxies. We
compared the abundances provided by the direct method with those obtained using
empirical calibrations, finding that (i) the Pilyugin method is the best
suitable empirical calibration, (ii) the relations between the oxygen abundance
and the N2 or the O3N2 parameters provided by Pettini & Pagel (2004) give
acceptable results for objects with 12+log(O/H)>8.0, and (iii) the results
provided by empirical calibrations based on photoionization models are
systematically 0.2-0.3 dex higher than the values derived from the direct
method. The O and N abundances and the N/O ratios are related to the
optical/NIR luminosity; the dispersion is consequence of the differences in the
star-formation histories. Galaxies with redder colours tend to have higher
oxygen and nitrogen abundances. Our detailed analysis is fundamental to
understand the nature of galaxies showing strong starbursts, as well as to know
their star formation history and the relationships with the environment.
