Don't call back, it's a SCAM.  In fact it's a good policy to never answer calls from persons or numbers you don't recognize and don't call back.  Here's some information from the real IRS on the scam as well as some news about the scam and a few people that have been caught.
https://www.irs.gov/uac/newsroom/irs-repeats-warning-about-phone-scams
http://www.forbes.com/sites/johnwasik/2016/06 ... u/#6cb8a18e171f
https://www.pindropsecurity.com/irs-phone-scam-live-call_analysis/
http://money.cnn.com/2016/05/25/news/irs-impersonators-scam/

Same here.. call back and hang up.. Jerks

This number called me and a recording said I was being sued by the IRS and I needed to return their call.

Claiming they are with IRS and we need to call them back... Never had this call/ problem before. I am speculating.... I gave funds to support Trump online now these people(ClintonFoundation) is trying to scare me or scam into giving to them...
FYI
IRS never calls you! They only send mail!

They're all criminals. Do not call them back and do not answer unknown calls.