They don't publish production numbers and the triple-alpha serial numbers makes them impossible to track.
They have been making them since 2009. My local Field & Stream had a grand opening special for $249.99, so I had to buy one. That store sold 1000 in the first day or two. I also have a couple M&P 15-22 Pistols, just because...
I think it's safe to say they total in the millions...
In the millions may be a bit high. It took Winchester over 35 years to produce a million model 94 lever guns and that's one of the most popular rifles ever made.