What is the way of writing very large numbers or small numbers in a short way?

Answer 1

Scientific notation.

For example instead of writing 1,234,000,000,000 using scientific notation this number can be written as:

1.234 * 10 12

Conversely, a small number such as 0.0000056 can be written as:

5.6 * 10-6

Hope that helps.