Officially there are 1024 GB in a terabyte, but using the rule that: 1000 GB is a TB, it makes calculations much easier.
It's the other way round. There are 1000 gigabites in a terrabite.
1024
There are 1024 megabites in 1 gigabite. 20 gigabites has 20,480 megabites.
a yottabite
It depends on how many gigabites it has like 8 gigabites can hold about 15 movies.
None
5500
4500
4,000,000,000
100
a half
1.306728 gb