IPv6 introduces a 128 bit IP address for both source and destination address fields.
This means that there are 2^128 addresses possible with that many bits.
2^128 is about 340,282,366,920,938,000,000,000,000,000,000,000,000
I have long contended that I have no idea how to read that number. I usually say something like "a lot".
But - thanks to one of my students (Thank You Bobby) the answer is now provided:
"Three hundred forty undecillion, two hundred eighty two decillion, three hundred sixty six nonillion, nine hundred twenty octillion, nine hundred thirty eight septillion."
One word - WOW!