I don't know what kind of calculator you have. Mine has 2 ENG keys (ENG stands for Engineering units) above the multiplication and division keys. So if I enter 405/65536 I will get
If I then press the SHIFT key and ENG (left) above the multiplication key I will get
which I think is what you are looking for. By the way, these keys are called Engineering units because they move the X 10 exponent to different multiples of 3, which is nice for converting things from meters to kilometers and millimeters and so forth.
If you don't have a key like that on your calculator you can try this little trick. When you get a result like
on your calculator, multiply by 10 raised to a power of one less than the absolute value of the exponent (in this case that would be 10 squared = 100) to get a number with no exponent, in this case
Of course then when you write that number down you have to remember to put the 2 leading zeroes back in to get