Seeing as my answer won't stop you getting lots of answers... I would have thought it's 一千七百万. I guess 十七百万 would be right but a bit odd to say, like "seventeen hundred" is in English (BrE at least). And I'd imagine 一千万七 means 10007000.

甚麼時候要念出 "零" 四位數字 為 一階 0 在各階之首位 或 中間 才需要念出 連串的 0 僅念一次即可 在 各階的 末位 ( ,***0 或 ,**00 或 *000 或 ,0000 ) 則不需要念出 1700,0000 一千七百萬 1070,0000 一千零七十萬 1007,0000 一千零七萬 1000,7000 一千萬七千 1000,0700 一千萬零七百 1000,0070 一千萬零七十 1000,0007 一千萬零七 1,0000,0007 一億零七 1,1000,0007 一億一千萬零七 1,0000,0000,0007 一兆零七 1,1000,0000,0007 一兆一千億零七 1,0000,1000,0007 一兆一千萬零七 1,1000,1000,0007 一兆一千億一千萬零七 其餘 見 http://www.italki.com/discussion/64389

一千七百万. It can't be pronounced as "十七百万", just as 1700 can't be pronounced as "十七百". 1700 can be pronounced as "一千七百", or "一千七" unless it is followed by a measure word. e.g. "多少钱?" "一千七(百)" or "一千七百元". but you can't say "一千七元" (It doesn't make sense) For the general rule for that, see http://www.cnshuxue.com/math/27/Article1341_1.htm

一千七百万

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