1014/(2x104) = 5 x 109.
More if you use 12.5 kilotons for Hiroshima. Or perhaps this talk was 10 years ago and Hawking was using 20 kilotons for Hiroshima. I've always heard 20 kilotons. In any event, way more than 10,000.
Agreed. But the articles says “100 megatons,” hence my comment.
Did I read that wrong? Going back to check ...
Nope, I read it correctly. :)