I know that for the numbers in the hundreds ending in "01" to "09" you use 零, such as
- 103 一百零三
- 509 五百零九
and so forth. Omitting the 零 here would change the meaning (一百三 = 130, 五百九 = 590).
How about numbers in the thousands ending in "001" to "009"? For example, how do you say 1001? Is it 一千零一 or 一千零零一?
Similarly, for 10001, is it 一万零一 or 一万零零零一?
Is 100000001 一亿零一 or 一亿零零零零零零零一?