Re: How many?
Well, it's slightly more fun than that, as sometimes "k" means 1024 and sometimes it means 1000 (particular if you're selling hard disk drives). (Also see job adverts - since when did "£10k" mean "£10,240"???)
So 1M can be any of 1000 * 1000, 1000 * 1024, 1024 * 1024 depending on context. And 1G is 1000 or 1024 times that.