Storing Integers Between 0 And About 808 Quadrillion -- Strings, Decimal, Or Variant?

I need to be able to precisely handle nonnegative integers (in the math sense of integer, not the VBA sense, of course) between the values of 0 and 808,035,046,350,570,000. (Don't ask.)

I'm wondering whether I should be handling these numbers in a string and do everything manually, or whether the datatype Decimal or Variant will work for me.

I read that Decimal handles +-79,228,162,514,264,337,593,543,950,335 with no decimal point, or +-7.9228162514264337593543950335 with 28 places to the right of the decimal.

I absolutely cannot have the "rounding type errors" and "oddities" that you get by storing integer values in doubles, for example, due to imprecission.

Seeing that Decimal seems to work in a decimal point manner worries me, that perhaps I shouldn't be using it for this scenario. However, it's range seems so much larger than what I need, I'm wondering if I would "get away" with it.

If needing no imprecission to creep in means that I have to use Strings and implement my own String math library, that's the route I would have to go.

Question 1 - If I need the numbers to be exact (again, nonnegative integers, no decimal points), do I need to use a String, or should I use a Decimal or Variant type?

Question 2 - What is the difference between Double and Variant, for the purposes of storing numeric values? I read that Doubles are 8 bytes, and Variants are 16 bytes, however the Variant description is "Any numeric value up to the range of Double", which confuses me since it's double the size.