> There is no actual "word" for million in Chinese.

> 百 is a hundred, 萬 is ten-thousand. A million is 百萬. But also I'm guessing 400萬 could be understood as the same as 4百萬/四百萬.

But there is 億 in Chinese which means a hundred million.

    　十       　             10 ten
    　百      　             100 hundred
    　千      　           1,000 thousand
    　萬      　          10,000 ten-thousand
    十萬     　          100,000 hundred-thousand
    百萬     　        1,000,000 million
    千萬     　       10,000,000 ten-million
    　億     　      100,000,000 hundred-million
    十億    　     1,000,000,000 billion
    百億    　    10,000,000,000 ten-billion
    千億    　   100,000,000,000 hundred-billion
    萬億 or 兆 1,000,000,000,000 trillion

萬 and 億 are traditional Chinese characters. The simplified characters are 万 and 亿 respectively.

兆 is usually avoided because it does not only mean trillion but also 百萬 (million) in mainland China's translation of "mega-byte" or "mega-pixel" for example.