how to write large numbers
Large numbers
a) We normally say a hundred, a thousand, a million. We only say one hundred, one thousand and one million when we want to emphasise the number:
What would you do if you won a million euros? (preferred to one million euros)
The city is about a hundred kilometres from the capital.
b) Numbers such as 100, 200, 1,000, etc. do not take a plural -s when we use them as determiners:
There were about two hundred people at the meeting.
c) However, we use the plural forms hundreds, thousands, millions + of + noun to refer to large, non-specific numbers:
It’s happened hundreds of times.
Millions of people live in poverty.
d) We often use commas in writing to separate long numbers of a thousand or more into each thousand part:
The repairs cost £1,250.
A total of $5,000,000 was spent on the project.