Aurora, as in the hospital in Wisconsin? If that's the case, I have the same question. Except I answered the second time they called and heard hello and then nothing so I hung up.
I have gotten calls from this number before, from different companies. From what i can tell it is a private line that companies can tap into. The local government uses this as well as large corporations (Froedtert Hospital). Its probably just a service these agencies pay for from the telephone company to hide identity, or help with spam calls/angry people calling back. I haven't tried to, but I'm sure if you call it back, it gives you a message around "this number is not accepting calls at this time."
I think, it is not a real working number. It is probably used by caller/any user of the phone to call out only. The phone is probably programmed to not accept call backs. It gives a busy signal whenever one calls back to that number.