Home Numbers & Operations Prime and Composite Numbers Prime and Composite Numbers Worksheets Here are more than 25 prime and composite number worksheets, carefully designed for grade 4 through grade 6 students. We will clearly discuss the concepts of prime, composite, co-prime, and twin prime numbers. We can classify all natural numbers as prime and composite. Prime Numbers: Any natural number that has only two factors, the number itself and 1 is known as a prime number. Eg. 1, 2, 3, 5,……11,……23,…..97,… The number 3 has only two factors. That is, it is only divisible by 3 and 1. (Without leaving a remainder). Thus 3 is a prime number. The number 2 is the smallest prime number. Interestingly, its the only even prime number which means all other prime numbers are odd. Composite Numbers: Any natural number that can be divided by other natural numbers and with the number itself and 1 is a composite number. Eg. 6, 8, 9,…..86,…99,… With 1 and 6, the number 6 has other factors like 2 and 3. Thus the factors of 6 are 1, 2, 3, and 6 which makes 6 a composite number. 1 is the only number which is neither prime nor composite. Twin primes: Prime number pairs which differ from each other by 2 are twin primes. Eg. 3 and 5, 11 and 13, 41 and 43….. In the above shown pair of numbers, the difference between the numbers is 2. Co-primes: Numbers that do not have any common factor other than 1 are called co-prime numbers. Eg. Number pairs 2 and 3, 3 and 4, 4 and 5…………17 and 23, 29 and 31,…….. 29 and 31 are both twin primes and co-primes. All twin primes are prime numbers, whereas all co-primes need not be prime numbers. Prime and Composite Numbers worksheets free download pdf