How to write 2 million USD?

I'm just curious, how do you properly write "2 million USD" in financial documents? I know it sounds basic, but I want to make sure I'm getting it right. Is it "2,000,000 USD" or "2 million USD" or maybe there's another way? It's just that I've seen it written differently in different places and I want to clarify the standard format. Could you please help me out with this? It's for an important financial report I'm preparing, and I want to make sure everything is accurate and professional. Thanks in advance for your assistance!