Do I need a Social Security number to buy bitcoin?

Excuse me, I'm a bit confused about the process of purchasing bitcoin. I've heard different things about the requirements, and I was wondering if you could clarify something for me. Specifically, is it necessary to have a Social Security number in order to buy bitcoin? I understand that some exchanges or services might have different rules, but I'm just trying to get a general understanding of the process. Could you shed some light on this for me?