Every integer n > 1 can be written uniquely (up to order) as a product of primes. Existence uses strong induction; uniqueness uses Euclid's Lemma.. The key formula is n = p₁^a₁ · p₂^a₂ · … · pₖ^aₖ. This concept is typically introduced in College. Understanding this concept builds a strong foundation for more advanced mathematics.