Worksheet: Prime and Composite Numbers

Q1:

What is a composite number?

Aa number with more than two factors
Ba number that has one factor repeated
Ca number with exactly two factors, 1 and itself
Da number with exactly two factors, 0 and itself
Ea number with exactly two factors, 0 and 1

Q2:

Is 21 a prime or a composite number?

Aa prime number
Ba composite number

Q3:

Is 23 a prime or a composite number?

Aa composite number
Ba prime number

Q4:

All prime numbers are odd except .

Q5:

Determine whether the number 85 is prime, composite, or neither.

Aprime
Bcomposite
Cneither prime nor composite

Q6:

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.

Q7:

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.

Q8:

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.

Q9:

What is the greatest prime number between 15 and 24?

Q10:

The table shows all the factors of some numbers.

Number	101	133	157	145
Factor of	1, 101	1, 7, 19, 133	1, 157	1, 5, 29, 145

Which of the numbers are prime?

A101 and 157
B157 and 145
C133 and 145
D133 and 157
E101 and 133

Q11:

Caribou calves weigh about 13 pounds at birth. Is the number 13 a prime or a composite number?

Aprime
Bcomposite

Q12:

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?

A
B
C
D
E

Q13:

Isabella bought these four raffle tickets, and one of them was the winning ticket.

The winning number is a prime number between 10 and 20. Which of her tickets won the prize?

Aticket number 34
Bticket number 23
Cticket number 18
Dticket number 15
Eticket number 17

Q14:

Which of the following is a prime number?

A43
B45
C8
D4

Q15:

Is 96 a prime number?

Ayes
Bno

Q16:

Are the numbers 2, 47, and 79 prime numbers?

Ano
Byes

Q17:

Which of the following is not a prime number?

A23
B73
C68
D2

Q18:

Find a prime number between 37 and 46.

Q19:

Look at these numbers.

How many of these numbers are prime?

Which is the largest prime number?

Which is the smallest composite number?

Q20:

State two prime numbers that are greater than 15 and less than 95.

A44, 60
B45, 61
C43, 59
D42, 58

Q21:

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

Q22:

Find the smallest prime number that is greater than 40.

Q23:

Which of the following integer sequences is not guaranteed to have infinitely many primes?

A
B
C
D

Q24:

How many prime numbers have integers as their square roots?

Q25:

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.