How many B707 derivatives are still in US service?

I was wondering if any one could help me figure out how many 707 derived aircraft (discounting the almost universal KC-135s) are today still being used by the US Military. E-3s Sentry, E-6s Mercury, E-8s JSTARS, test aircraft and other strictly cargo and pax aircraft… It´s a fact that the veteran VC-137s were all retired, right? Also how many civilian 707swere purchased second hand and broken up for re-use of their more efficient JT-3 engines.

Best Regards

Hammer