Working and calculating with 16+ digit numbers

Hi,

I am encountering an issue with working with 16 + digit numbers.

I have a script that converts the number from figures to words. However I use a math.floor calculation on the figures to separate out the decimals it rounds incorrectly.

Is there a simple way to deal with such long numbers.  Or am I going to have to deal with this in the scrip and take out the Quadrillion values and compute them separately.

Would share the script but it is on my work computer.