one slash...

try over or by

...in one (pause) two hundred ninety-nine million, seven hundred ninety-two thousand, four hundred fifty-eigths

It's a fraction - you'd have to read it sort of like you'd read 1/3 as one third or 3/8 as three eighths. And that's pretty cumbersome with a number like that.

Othewise, I'd say "one over two hundred..." 

You don't even need a native speaker to confirm it.  It is definitely not spoken as slash.  The most probable situation you will hear it pronunced as slash is in URLs, e.g. www.englishforums.com/English is pronounced as www dot englishforums dot com slash English.

Not all software are so dumb.  Opera has a plug-in that can read out the English text on a webpage.  It says, ". . . in a vacuum in -PAUSE- one divided by two hundred ninety-nine million, seven hundred ninety-two thousand, four hundred fifty-eight -PAUSE- of a second".  The voice function of Opera is the most intelligent I've ever seen and the pronunciation is much better than other machine-like voice synthesizers.  Give it a try.

Sorry, I didn't mean that.  I certainly agree with you that even the most advanced software cannot come even close to human in many aspects.  I was just saying one software is better than the other. Programming a software to say "one divided by" or "one third" when there is a fraction is well within the reach of current technology.  It is surprising that many text-to-speech software are still so primitive.

AI field?  That's a very interesting subject.  But there seems to be no breakthrough in recent years as far as I know.  Or perhaps I was just not noticing?