The Pro, which has a 12.9-inch screen and is aimed at creative professionals, launched in late November and starts at $799 (£679) in the US.
The sales data does not come from Apple.
By way of comparison, the iPad Air 2 shipped 557,000 units in the first four weeks of sales, according to TalkingData. The iPad mini 4, which went on sale before the Pro, shipped around 100,000 units. Both of these models are cheaper than the Pro.
The launch of the iPad Pro has not been without hiccups. The Pencil and Smart Keyboard accessories were advertised heavily alongside the tablet but supply constraints meant that shipping times slipped to 4-5 weeks. This, in turn, lead to unhappy customers who were left with a giant iPad and none of the tools to use it.
China is fast becoming one of Apple's biggest markets, generating the company over $13 billion (£8.7 billion) during the third quarter of 2015. That was up from $6 billion (£4 billion) during the same period in 2014.
Apple CEO Tim Cook rhetorically asked in an interview why anyone would buy a PC anymore, and the iPad Pro is positioned as a PC replacement that sits between a tablet and a laptop.