2**10 x 2**10 x 2**10 > 10**9
1024 x 1024 x 1024 > 1,000,000,000
Now that is not even 32 bits
So 2 ** 60 (just 60 bits) > (10 ** 9) * (10 ** 9) = 10 ** 18
If you count the digits, then you 5 digits(billions) + 9 (hundreds of millions) + 2 (cents).
This is only 16 digits.
There are 18 digits in 2 to the 60th (2 ** 60) (at least).