8. How many prime numbers are there in the list
$$
1,12,123,1234,12345,123456 ?
$$

A 0
B 1
C 2
D 3
E 4
Solution
A It is important to remember that we do not regard 1 as a prime number.
We see that 12,1234 and 123456 are not prime numbers becauses they are divisible by 2. Also, 123 is not a prime number because it is divisible by 3 , and 12345 is not a prime number because it is divisible by 5 .
So there are no prime numbers in the list.