Just came across this free app in the App Store. It gives you a keyboard with numbers. And letters all available without switching. You can only use it inside it's own app but the copy all button allows you to copy and paste into any other app really easily. One thing worth noting, when you press copy all button there is no indication that anything has been copied........but it has!
Oh yeah, just to say, I have no connection to the app or it's developers, I just think that it is quite useful.