AMC12 Number Theory 2

Question 1

What is the sum of all positive divisors of 28?

Accepted Answer

56

Answer

28

Answer

42

Answer

14

Question 2

How many two-digit prime numbers exist?

Accepted Answer

21

Answer

15

Answer

25

Answer

18

Question 3

What is lcm(12, 18)?

Accepted Answer

36

Answer

6

Answer

72

Answer

216

Question 4

For which prime p is p^2+2 also prime?

Accepted Answer

3

Answer

2

Answer

5

Answer

7

Question 5

What is the units digit of 7^53?

Accepted Answer

7

Answer

3

Answer

9

Answer

1

Question 6

How many perfect squares are strictly between 100 and 400?

Accepted Answer

9

Answer

8

Answer

10

Answer

12