Which of the following numbers is prime?

133
143
153
163

Question

Which of the following numbers is prime? 

       133
       143
       153
       163

anonymous · Answer

163 is prime

bananas1234 · Answer

could you explain how you got that?

thesmartone · Answer

To see if it is divisible by 3

add up all the numbers, and if the sum of it is divisible by 3, then the number is divisible by 3.

bananas1234 · Answer

so for example see if 133 is divisible by 3?

bananas1234 · Answer

and then test the rest of the options?

thesmartone · Answer

1+3+3 = 7

So it is not divisible by 3

doesn't end in 5, or 0 not divisible by 5

Divisible by $\sf 7$

So it is not a prime.

thesmartone · Answer

153 is divisible by 3, so that is also eliminated

1+5+3 = 9
which is divisible by 3

thesmartone · Answer

143

not divisible by 3, 5, 7, 

and then aha! Divisible by 11

thesmartone · Answer

and all of these are not divisible by 2 because they are all odd.

thesmartone · Answer

So now do you get how 163 is the answer? :P

bananas1234 · Answer

sorry i had to step away for a minute, yes i think i understand that....Thanks!!  @TheSmartOne