You can write 90 in short word form as ninety.
You can also write say if your name is Suphil. Then you can write as Er. Suphil or even Eng.Suphil . Both are accepted.
6.02 in short word form is: six and two hundredths.
Use an abbreviation...
Three and sixty-five thousand seven hundred sixty-two hundred-thousandths.
1,507,099 in short word form is 1 million, 507 thousand and 99.