The lowest whole number with six digits is 100,000, which is greater than 99,999, the greatest whole number with five digits. A whole number is defined as any integer that is zero or greater, meaning that it does not contain fractions.

The set of whole numbers does not include negative numbers. If the question considers the set of integers rather than whole numbers, the lowest six digit integer would be -999,999. Since the greatest integer with five digits would remain 99,999, the answer to the question would change. The set of whole numbers is also known as natural numbers. The similar set of counting numbers is identical to the whole number set, except for the exclusion of zero in the counting numbers set.