是2 million 还是2 millions?

是2 million 还是2 millions? 是millions of people 还是million people 具体是several millions of students还是several million students several millions of 还是several million 为什么左边标注millions?million不是不应该加s吗?像2 million? 是several millions of the students还是several million of the st several million people还是several millions of people问什么 millions and million是什么意思 million thousand hundred millions millions of与million million million of millions和millions of的区别! millions of 、 million of 、 millions 、a million 的区别