It's incredibly fascinating how very simple constructs like primes have such complexity to them. It's very easy for a 14 year old to formulate questions relating to primes that noone can answer.

what I find interesting is the amount of computing power that it takes to calculate.

Edit: As an after thought, there are recordings of million digit prime numbers: http://www.primegrid.com/download/SR5-180062.pdf

Are there chains of Sophie Germain primes?

e.g.,

    p is prime
    2p + 1 is prime
    2(2p + 1) + 1 is prime...

this is a great example of the title change rule making a title worse

i think taglines/subtitles/subject sentences should be eligible for titles too