Last visit was: 23 Apr 2026, 22:18 It is currently 23 Apr 2026, 22:18
Home
Messages
Tests
Schools
Events
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Apr 2026
Posts: 109,800
Own Kudos:
810,888
 [4]
Given Kudos: 105,867
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,800
Kudos: 810,888
 [4]
Which of the following numbers is prime? 06 Apr 2018, 04:38
Kudos
Add Kudos
4
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

35% (medium)

Question Stats:

67% (01:38) correct 33% (01:38) wrong based on 335 sessions

History

Date
Time
Result
Not Attempted Yet
Which of the following numbers is prime?

A. 117
B. 133
C. 189
D. 209
E. 223
ShowHide Answer
Official Answer
E
Most Helpful Reply
avatar
VincentJongen
avatar
Joined: 30 Jan 2018
Last visit: 12 Apr 2018
Posts: 4
Own Kudos:
9
 [8]
Posts: 4
Kudos: 9
 [8]
Which of the following numbers is prime? 09 Apr 2018, 09:23
6
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
117 is divisible by 3, as 1+1+7 = 9
133 is divisible by 7, as 140-7 = 133
189 is divisible by 3, as 1+8+9 = 18
209 is divisible by 11, as 220-11 = 209

So therefore I think that 223 is prime (E)
General Discussion
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 23 Apr 2026
Posts: 109,800
Own Kudos:
810,888
 [2]
Given Kudos: 105,867
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,800
Kudos: 810,888
 [2]
Which of the following numbers is prime? 06 Apr 2018, 04:39
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
Bunuel
Which of the following numbers is prime?

A. 117
B. 133
C. 189
D. 209
E. 223
Show more

Similar questions:
https://gmatclub.com/forum/which-of-the ... 68179.html
https://gmatclub.com/forum/which-of-the ... 31816.html
User avatar
Vaibhav708
User avatar
Joined: 27 Feb 2021
Last visit: 02 Dec 2024
Posts: 3
Own Kudos:
2
 [1]
Given Kudos: 3
Posts: 3
Kudos: 2
 [1]
Which of the following numbers is prime? 03 Aug 2022, 07:53
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
There is an easier way to find prime numbers. First find the square root of nearest and lowest perfect square. If none of the prime numbers till that square root divides the given number, then it is a prime number.

Nearest root of 117 is 10. 117 is divisible by 3. Not a prime no.
Nearest root of 133 is 11. 133 is divisible by 7. Not a prime no.
Nearest root of 189 is 13. 189 is divisible by 3. Not a prime no.
Nearest root of 209 is 14. 209 is divisible by 11. Not a prime no.
Nearest root 223 is 14. No prime lower than and equal to 14 divides 223.
Therefore 223 is a prime number.(E)
User avatar
7Amulya
User avatar
Joined: 28 Mar 2022
Last visit: 16 Apr 2026
Posts: 23
Own Kudos:
2
Given Kudos: 554
Posts: 23
Kudos: 2
Which of the following numbers is prime? 05 Apr 2025, 23:15
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hi Vaibhav708,

Please elaborate step by step. I am not able to figure out how you did this.
Vaibhav708
There is an easier way to find prime numbers. First find the square root of nearest and lowest perfect square. If none of the prime numbers till that square root divides the given number, then it is a prime number.

Nearest root of 117 is 10. 117 is divisible by 3. Not a prime no.
Nearest root of 133 is 11. 133 is divisible by 7. Not a prime no.
Nearest root of 189 is 13. 189 is divisible by 3. Not a prime no.
Nearest root of 209 is 14. 209 is divisible by 11. Not a prime no.
Nearest root 223 is 14. No prime lower than and equal to 14 divides 223.
Therefore 223 is a prime number.(E)
Show more
User avatar
Krunaal
User avatar
Tuck School Moderator
Joined: 15 Feb 2021
Last visit: 21 Apr 2026
Posts: 853
Own Kudos:
912
 [2]
Given Kudos: 251
Status:Under the Square and Compass
Location: India
Schools: Tuck '26 (WL) Ross '26 (A$$$$) Stern '26 (A) McCombs '26 (A$)
GMAT Focus 1: 755 Q90 V90 DI82
GPA: 5.78
WE:Marketing (Consulting)
Products:
My Reviews
Schools: Tuck '26 (WL) Ross '26 (A$$$$) Stern '26 (A) McCombs '26 (A$)
GMAT Focus 1: 755 Q90 V90 DI82
Posts: 853
Kudos: 912
 [2]
Which of the following numbers is prime? 06 Apr 2025, 12:00
1
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
7Amulya
Hi Vaibhav708,

Please elaborate step by step. I am not able to figure out how you did this.
Vaibhav708
There is an easier way to find prime numbers. First find the square root of nearest and lowest perfect square. If none of the prime numbers till that square root divides the given number, then it is a prime number.

Nearest root of 117 is 10. 117 is divisible by 3. Not a prime no.
Nearest root of 133 is 11. 133 is divisible by 7. Not a prime no.
Nearest root of 189 is 13. 189 is divisible by 3. Not a prime no.
Nearest root of 209 is 14. 209 is divisible by 11. Not a prime no.
Nearest root 223 is 14. No prime lower than and equal to 14 divides 223.
Therefore 223 is a prime number.(E)
Show more
For option A. and C., the sum of the digits is multiple of 3 => so the numbers have to be divisible by 3, they cannot be prime.

The rest can be checked by the following method: Verifying the primality of a given number \(n\) can be done by trial division, that is to say dividing \(n\) by all prime integers smaller than \(\sqrt{n}\) (if \(\sqrt{n}=integer\) then n is obviously not a prime), thereby checking whether \(n\) is a multiple of \(prime<\sqrt{n}\).

Verifying the primality of \(133\): \(\sqrt{133}\) is little less than \(12\). We should check \(133\) on divisibility by prime numbers from 2 to 12: \(133\) is divisible by \(7\), hence \(133\) is not prime.

Verifying the primality of \(209\): \(\sqrt{149}\) is little more than \(14\). We should check \(209\) on divisibility by prime numbers from 2 to 14. \(209\) is divisible by \(11\), hence \(209\) is not prime.

Option E. has to be the answer.

Verifying the primality of \(223\): \(\sqrt{223}\) is little less than \(15\). We should check \(223\) on divisibility primes from 2 to 15. \(223\) is not divisible by any of the integers from \(2\) to \(15\), hence \(223\) is prime.
Moderators:
Bunuel
Math Expert
109795 posts
Krunaal
Tuck School Moderator
853 posts