Can a composite number be negative?

By standard mathematical convention, composite numbers are defined only for positive integers greater than 1, which means negative numbers are not classified as composite. The formal definition focuses on the positive divisor structure of natural numbers, and extending this classification to negative integers creates unnecessary complications without adding mathematical value. When we say "composite number," we specifically mean numbers like 4, 6, 8, 9, and so on—all positive values that have more than two positive divisors.

However, the concept of factorization does extend to negative integers in broader contexts. A negative number like -12 can certainly be factored as (-2) × 6 or (-3) × 4, and these factorizations are meaningful in algebraic manipulation and equation solving. The key distinction is that while we can factor negative numbers, we don't label them as "composite" because the classification system for prime and composite numbers was designed specifically for the natural numbers (positive integers). This convention keeps number theory clean and consistent—when mathematicians discuss properties of composite numbers, they're working within a well-defined framework where all numbers are positive. In practical applications like programming, you'll typically work with absolute values when applying composite number tests, then handle the sign separately as needed for your specific use case.