525 = 525/1, although I see no reason why anyone would wish to write it like that.
525 = DXXV
525 = quinientos veinticinco
I would write it as 2.06 million - exactly as in the question.
You would write it as 60,000,000
You would write it as.... 34,500,000
IT would be written as four hundred million.
$525 million USD
You would write 3.1 million dollars in numerals like this: 3,100,000