What next to trillion?

Answer 1

In US usage, the next named number after one trillion is one quadrillion.

One trillion is 1,000,000,000,000 or 1012.

One quadrillion is 1,000,000,000,000,000 or 1015.

However, in traditional British usage (which is used in much of the world, but no longer in official British government documents):

One trillion is 1,000,000,000,000,000,000 or 1018.

One quadrillion is 1,000,000,000,000,000,000,000,000 or 1024.

It is important to understand these differences if you are going to be writing something that may be seen outside of your own country or if you are reading something written outside your own country.