Did you know that there is a number that, if you were in possession of it, could land you in jail for a very long time? Well, there is – and here's why it could get you into serious trouble ...

It's all about prime numbers and how they are used for encryption on things such as DVD encoding and online banking portals. The way encryption works is probably best explained in the video, but here's a quick lesson.

You get given a public key, which is a number that is the sum of two prime numbers. When you log in to your online banking, your public key is handed over to the bank, where it then checks that the two prime numbers (or private key) add up to your public key number. Confused much? Seriously, the video explains it a lot better than I can.  

Anyway, the number in question is the prime number that, once discovered, was responsible for breaking the codes that prevented DVDs from being copied. This number made it possible for you to download illegal copies of films – not that any of you have done that, of course! So, as I said, the video is quite interesting and I certainly learned a thing or two from it. Hope you enjoy it!