Apply Prime Number Knowledge and Factorization

1) Which number is the largest prime under 100?

91

95

99

97

The largest prime number under 100 is 97.

Explanation

The largest prime number under 100 is 97.

2) What is the prime factorization of 32?

2 × 16

2 × 2 × 2 × 2 × 2

4 × 8

2 × 4 × 4

The prime factorization of 32 is 2 × 2 × 2 × 2 × 2.

Explanation

The prime factorization of 32 is 2 × 2 × 2 × 2 × 2.

3) Which of the following is prime?

91

97

99

100

The number 97 is prime because its only factors are 1 and 97.

Explanation

The number 97 is prime because its only factors are 1 and 97.

4) Which number is not prime?

101

103

105

107

The number 105 is not prime because 105 = 3 × 5 × 7.

Explanation

The number 105 is not prime because 105 = 3 × 5 × 7.

5) Which is a composite number?

113

121

127

131

The number 121 is composite because 121 = 11 × 11.

Explanation

The number 121 is composite because 121 = 11 × 11.

6) Which is the correct prime factorization of 45?

3 × 3 × 5

9 × 5 × 1

3 × 15

45 × 1

The prime factorization of 45 is 3 × 3 × 5.

Explanation

The prime factorization of 45 is 3 × 3 × 5.

7) Which prime factorization is correct for 100?

2 × 10 × 5

2 × 2 × 5 × 5

20 × 5

4 × 25 × 1

The prime factorization of 100 is 2 × 2 × 5 × 5.

Explanation

The prime factorization of 100 is 2 × 2 × 5 × 5.

8) Which number is prime?

33

41

45

49

The number 41 is prime because its only factors are 1 and 41.

Explanation

The number 41 is prime because its only factors are 1 and 41.

9) Which of these numbers is composite?

39

43

47

53

The number 39 is composite because 39 = 3 × 13.

Explanation

The number 39 is composite because 39 = 3 × 13.

10) Which prime factorization is correct for 24?

2 × 12

6 × 4

2 × 2 × 2 × 3

8 × 3 × 1

The prime factorization of 24 is 2 × 2 × 2 × 3.

Explanation

The prime factorization of 24 is 2 × 2 × 2 × 3.

11) Which is prime?

85

89

91

95

The number 89 is prime because its only factors are 1 and 89.

Explanation

The number 89 is prime because its only factors are 1 and 89.

12) Which number is composite?

63

67

71

73

The number 63 is composite because 63 = 7 × 9.

Explanation

The number 63 is composite because 63 = 7 × 9.

13) Which numbers are prime?

12, 14, 15

13, 17, 19

20, 22, 25

27, 30, 32

These numbers are prime because each has only two factors.

Explanation

These numbers are prime because each has only two factors.

14) Which two numbers are prime?

35 and 37

39 and 41

41 and 43

45 and 47

Both 41 and 43 are prime numbers.

Explanation

Both 41 and 43 are prime numbers.

15) Which of the following numbers is prime?

123

125

129

127

The number 127 is prime because its only factors are 1 and 127.

Explanation

The number 127 is prime because its only factors are 1 and 127.

16) Which of the following is prime?

169

173

175

177

173 is prime because it has only two factors: 1 and 173.

Explanation

173 is prime because it has only two factors: 1 and 173.

17) Which of these numbers is not prime?

131

137

133

139

18) Which number is prime?

141

149

153

155

The number 149 is prime because its only factors are 1 and 149.

Explanation

The number 149 is prime because its only factors are 1 and 149.

19) Which number is prime?

109

111

115

119

The number 109 is prime because its only factors are 1 and 109.

Explanation

The number 109 is prime because its only factors are 1 and 109.

20) Which of these numbers is composite?

157

163

161

167

The number 161 is composite because 161 = 7 × 23./

Explanation

The number 161 is composite because 161 = 7 × 23./

Applying Prime Number Knowledge

1) Which number is the largest prime under 100?

2) What is the prime factorization of 32?

3) Which of the following is prime?

4) Which number is not prime?

5) Which is a composite number?

6) Which is the correct prime factorization of 45?

7) Which prime factorization is correct for 100?

8) Which number is prime?

9) Which of these numbers is composite?

10) Which prime factorization is correct for 24?

11) Which is prime?

12) Which number is composite?

13) Which numbers are prime?

14) Which two numbers are prime?

15) Which of the following numbers is prime?

16) Which of the following is prime?

17) Which of these numbers is not prime?

18) Which number is prime?

19) Which number is prime?

20) Which of these numbers is composite?