I'm a practicing CPA. A friend got one of these calls today from this number. It is a scam. The IRS never initiates collections by phone -- letters are sent first followed by more letters and then certified letters if one doesn't respond. One can also report the scam to one's state's Attorney General. Never, under any circumstance, volunteer any personal information to these scammers.
Got the same call as everyone else on here. Saw that it seemed to have started recently and decided to report it. The FTC website is super easy to report this sort of stuff!