57.5
Eight
646,592,112
398
34.38461538461538
512,996 = five hundred twelve thousand, nine hundred ninety-six.
The number 690 is spelled "six hundred ninety" or "six hundred and ninety."
394 / 6 = 65.66667
Thirty-six million, five hundred ninety thousand, twelve.
55.583 recurring
one hundred and ninety six
If I was talking in term of currency, I would say, "twelve thousand, eight hundred, ninety-six dollars and seven cents." In plain numbers, I would say "twelve thousand, eight hundred, ninety six, point zero seven."
396.696 = three hundred ninety-six and six hundred ninety-six thousandths.