987,654,321
Nine hundred and eighty-seven million six hundred and fifty-four thousand three hundred and twenty-one.

10,400
ten thousand four hundred （對）
ten thousands four hundreds （錯）

345
英式：three hundred and forty-five
美式：three hundred forty five

百萬 = million
My hometown has 6 million people.
我家鄉有6百萬人。

十億 = billion
The population of China is about 1.3 billion. How about England？
中國人口大概13億，英國呢？

fractions 分數
2/3的三種方式：
1.two-thirds
2.two over three
3.two divided by three

Generally, in British English we usually connect large numbers with double or single digit figures with and, but in American English and is not used.
通常情況下，英式英語當中，百位和十位要加上and，而在美式英語中不用。
The facial mask brand I use is also used by two-thirds of my friends.
我用的這個面膜牌子，我三分之二的朋友也在用。