More important than knowing what 4x6 is, is understanding what multiplication is, why division is really the same operation, understanding commutative, associative, distributive properties of operations, etc. All of this comes as a result of repeated drilling of multiplication problem sets. Once this has been assimilated, you can move on to more abstract concepts that build on that foundation, and at that point sure you can use a calculator to work out the product of two integers as a convenience.
