A prime nummer (or a prime) is a naitural nummer greater nor 1 that haes na positive divisors ither nor 1 an itself. A naitural nummer greater nor 1 that is nae a prime nummer is called a composite nummer. For example, 5 is prime acause anly 1 an 5 evenly divide it, whauras 6 is composite acause it haes the divisors 2 an 3 in addeetion tae 1 an 6. The fundamental theorem o arithmetic establishes the central role o primes in nummer theory: ony integer greater nor 1 can be expressed as a product o primes that is unique up tae orderin. The uniqueness in this theorem requires excludin 1 as a prime acause ane can include arbitrarily mony instances o 1 in ony factorization, e.g., 3, 1 × 3, 1 × 1 × 3, etc. are aw valid factorizations o 3.