Translation:Seven secretaries work with the judge.
The numbers for counting people (beirt go deichniúr) are all nouns. They take the Ginideach Iolra after them. Beirt is also feminine so you add a seimhiú onto the next noun. You'll need to know the tréaniolra and lagiolra for these.
Beirt- Beirt fhear, Beirt mhúinteoirí.
Triúr- Triúr fear, Triúr múinteoirí.
Ceathrar- Ceathrar fear, Ceathrar múinteoirí.
The joys of the Tuiseal Ginideach, Hollywood will have to make a horror film out of it.
As stated above, the genitive plural is traditionally used but that the nominative singular can be used with exceptions.
Addendum: from p168 of the standard (available here: http://www.oireachtas.ie/parliament/media/Final-Version.pdf) is é an ginideach iolra den ainmfhocal a leanann an uimhir phearsanta. So, genitive plurals only in the course, please, but who knows what you may encounter in the wild.