I took ACRP's certification exam (which I personally think is a little bit more recognized in the for-profit industry, while CCRP is a little better in university settings) and I got through it painlessly. It's pretty easy when you've been a good worker for a few years.
You do NOT need to memorize each number. You should know the basics like 21CRF50 covers informed consent while 21CRF812 covers device, but you won't need to know the exact citation.
Don't concentrate on memorizing the regulations, you need to know how the regulations translate into PRACTICE. When you read the regulation, stop and think, "Okay, this regulations says that I need to do X... HOW do I make sure my site can prove it is compliant in the real world?"