I couldn't find any info on annunities, but if you divide 1.6B by 25 years, that's still 64M a year. Even if you lose half to taxes...!
It's hard to comprehend how much 1,000,000,000 is, even compared to a million.
(for those interested, this is my favourite demonstration of the difference:
https://youtu.be/8YUWDrLazCg )