I would read it first as "fifteen and a bunch of zeros."
If someone really cares what the value of this number is, they would need to mark it off with commas so that the place values are more clear.
  

1,500,000

Oh, now I see--it is one and a half million, or one million five hundred thousand if you prefer. Most times, when you are reading numbers like this in a text, you don't care that much about the details after the first couple of digits. Of course, if you are an accountant reading it on a balance sheet, then the details may matter down to the last dollar or pound or euro.