Prime time

I've been looking at some big numbers today, after my latest crude attempt to calculate the hypervolume of cosmic history in Planck units. This seems to me to be the biggest number that could have any actual physical significance (as distinct from statistics or pure number theory) - but that's for me to claim and you to dispute. It's a 243-digit number, and probably begins with a 7. I want to post something on this later, because I've got this slightly crazed idea that people should know these things, and after much Googling I still haven't yet found anyone who's worked it out and shared it.

Meanwhile, here's a much bigger number than that, with (surely) no physical significance at all. Someone has actually written down the largest known prime number in words. How silly?

If I ever get round to part 2 of the cube story, which will deal with altogether vaster numerical realms, I'll try and put this into perspective.

But that will have to wait.
Maybe a very, very long time...