Prime Numbers

Numbers that are only divisible by 1.
I can give you the first 100 prime numbers, just because I'm not totally ignorant.

But explain to me why I need to know this?
Is there anyone out there that uses this knowledge on a regular basis?

I'm almost 40 and I've never once needed to recall the definition of a PRIME NUMBER unless I was helping one of my lovely children with their homework.

Sometimes it's hard to answer the question, "Why do I need to know this in real life?"