h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

This is great! I may read all of it eventually, but a quick browse is rewarding.

Three things come to mind though:

1 We would like to know the name of the American professor who said "two is odd because it is even" -- or if we can't find it, we needn't be bothered to know that he was American or a professor.

2 You mention without comment the fact that the first line of a number square is all you need check for factors of all the rest. A moment's reflection showed me why, because I already knew that one of two or more factors must be less than or equal to the square root; but for the general reader a word of explanation might be helpful. Otherwise why write them into a square?

3 Second last paragraph: "The process of factoring a large number to determine its prime-number components presents a formidable computational challenge. Indeed, it is virtually impossible!" Virtually impossible means possible, particularly to a mathematician. This is just sloppy writing! It takes a very big computer, but it is perfectly doable, and this is a matter of contention internationally, I gather. The Americans insist that everyone else restrict their encryption primes to a certain size, precisely so that they can crack them.