0
21 is divisible by 3 and 7, so it is composite. 91 is divisible by 7 and 13, so it is composite. 51 is divisible by 3 and 17. 31 is divisible by only 1 and itself, so it is the Prime number.
Still curious? Ask our experts.
Chat with our AI personalities
LaoThe path is yours to walk; I am only here to hold up a mirror.
Chat with Lao
JordanLooking for a career mentor? I've seen my fair share of shake-ups.
Chat with Jordan
MaxineI respect you enough to keep it real.
Chat with MaxineAdd your answer:
Earn +20 ptsQ: Which number is prime out of 91 51 31 21?
Write your answer...
Submit
Still have questions?
Trending Questions
Fruit a red eared slider will eat?
All prisms are Platonic solids?
What is an example of a short story with a moral lesson?
What is making a squeaking chirping scraping noise at belt side of engine on 2001 ford windstar pulley tensioner water pump alternator and power steering pump have been replaced and noise is the same?
The formula for finding the volume of a cylinder?
How did Africans slaves contribute to the development of the Africans?
Were urban political machines evil?
Founder of Bank of America?
What does the letter M mean in roman numerals?
Where is St Basil's Cathedral?
Where is the Dogs Only Inc in Little Rock Arkansas located?
What is the hardest part of the vegetable to eat?
What was the result of the Renaissance?
How many times have the Pittsburgh Steelers made the playoffs after winning the Super Bowl?
What is the average speed of a car that traveled 750 miles in fifteen hours?
Can a corporation give a car as a gift?
Which country have capital named Zurich?
What do fire ants eat sour or sweet?
Muscles that help the skeleton move are?
The yearly movement of the earth around the sun is?
Copyright ©2025 Infospace Holdings LLC, A System1 Company. All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Answers.