Worksheet: Prime and Composite Numbers
In this worksheet, we will practice deciding whether a number is prime or composite.
Is 21 a prime or a composite number?
- Aa prime number
- Ba composite number
Is 23 a prime or a composite number?
- Aa composite number
- Ba prime number
All prime numbers are odd except .
Determine whether the number 85 is prime, composite, or neither.
- Cneither prime nor composite
Michael is learning about prime numbers. He knows that 5 is a prime number, because the only factors of 5 are 1 and 5.
Is 9 a prime number? Why?
- AYes, because its only factors are 1 and 9.
- BNo, because 3 is a factor.
Benjamin says that 1 is a prime number because it only has 1 factor pair.
Is he correct? Why?
- AYes, 1 only has one factor.
- BNo, because all odd numbers are prime.
- CNo, prime numbers have more than two factors, 1 only has one factor.
- DNo, prime numbers have two factors, 1 only has one factor.
- EYes, because all odd numbers are prime.
Madison says that every even number is composite because 2 is a factor.
Is she correct? Why?
- AYes, because all odd numbers are prime.
- BYes, because 2 is even and composite.
- CYes, because 2 is an even number.
- DNo, because 2 is even and composite.
- ENo, because 2 is even and prime.
A teacher asked her class to color all the prime numbers between 1 and 10. Here are some of their answers. Which one is correct?
Isabella bought these four raffle tickets, and one of them was the winning ticket.
- Aticket number 34
- Bticket number 23
- Cticket number 18
- Dticket number 15
- Eticket number 17
Which of the following is a prime number?
Is 96 a prime number?
Are the numbers 2, 47, and 79 prime numbers?
Which of the following is not a prime number?
Find a prime number between 37 and 46.
Look at these numbers.
How many of these numbers are prime?
Which is the largest prime number?
Which is the smallest composite number?
State two prime numbers that are greater than 15 and less than 95.
- A44, 60
- B45, 61
- C43, 59
- D42, 58
All odd numbers greater than 7 can be expressed as the sum of three prime numbers. Which three prime numbers have a sum of 97?
- A17, 19, 61
- B17, 18, 62
- C16, 20, 61
- D18, 19, 60
Find the smallest prime number that is greater than 40.
How many prime numbers are there, and why?
- AWe do not know, because computers are not powerful enough to compute as largely as we need.
- BInfinitely many in theory, as you could theoretically extend the sieve of Eratosthenes indefinitely.
- CInfinitely many, otherwise you could simply take the product of all of them and add one.
- DFinitely many, because once you reach a certain size, every number factors into smaller primes.