Sorry, you may have got an A+ in American English, but in British English it´s only an A-. (But still a good grade!!)

 We would normally say "and" between the hundred and the eighty, and "and sixteen" at the end.

Think of it like we say all the millions, putting in any "and" where necessary, then we do the same with the thousands, then we do the same with what´s left over.

We might also put in commas after million and thousand.

We would also normally hyphenate eighty-three

So:

Thirteen million, nine hundred and eighty-three thousand, eight hundred and sixteen.

The commas are optional.

525983816 would be

Five hundred and twenty-five million, nine hundred and eighty-three thousand, eight hundred and sixteen.

The same principle goes when adding 3 more significant figures:

133525983816 would be

One hundred and thirty-three billion, five hundred and twenty-five million, nine hundred and eighty-three thousand, eight hundred and sixteen.

etc.

Marion,

Thanks for this info. But I cannot still get it through. There is a question somewhere and I tried all of the following but all of them are rejected.

Thirteen million, nine hundred and eighty-three thousand, eight hundred and sixteen
Thirteen million nine hundred and eighty-three thousand eight hundred and sixteen
THIRTEEN MILLION NINE HUNDRED AND EIGHTY-THREE THOUSAND EIGHT HUNDRED AND SIXTEEN
THIRTEEN MILLION NINE HUNDRED EIGHTY-THREE THOUSAND EIGHT HUNDRED AND SIXTEEN
THIRTEEN MILLION NINE HUNDRED EIGHTY THREE THOUSAND EIGHT HUNDRED SIXTEEN
THIRTEEN MILLION, NINE HUNDRED AND EIGHTY-THREE THOUSAND, EIGHT HUNDRED AND SIXTEEN

Question text is:

In the game of lottery 6 different numbers are chosen among 49. How many different combinations are there? Provide a formal(textbook-like) answer.

And I am very sure of the number.

? binomial(49,6)
%1 = 13983816

does the answer have to be written as words? That seems strange to me.  Commas are used to separate the digits:

13,983,816

I also tried it but no, it´s not accepted.

I just don´t understand what does "Provide a formal(textbook-like) answer." mean actually??

Perhaps they want you to provide the formula you used in order to calculate the answer.