I got a call saying the IRS is suing me and to call back, but the call back number is not a working number.

That's because it's a spoofed number and this is a SCAM.  Here's some information from the real IRS as well as some info from news sources:
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/