How many digits in a billion billion?

Answer 1

In the US:

1 billion = 109

1 billion billion = 1018

That's '1' followed by 18 zeros, for a grand total of 19 digits.

But in the UK:

1 billion = 1012

1 billion billion = 1024

That's '1' followed by 24 zeros, for a grand total of 25 digits.