Q. 84.6( 25 Votes )

Which of the following numbers are prime?

(a) 23 (b) 51

(c) 37 (d) 26

Answer :

(a) 23 is a prime number;


23 = 1 × 23


23 = 23 × 1


Prime numbers are the numbers that can be divided by 1 and by number itself. So, 23 has two factors 1 and 23. It is a prime number.


(b) 51 is a composite number,


51 = 1 × 51


51 = 3 × 17


51 = 17 × 3


51 = 51 × 1


So, it has four factors, 1, 3, 17, and 51. Therefore it is a composite number not a prime number.


(c) 37 is a prime number,


37 = 1 × 37


37 = 37 × 1


Prime numbers are the numbers that can be divided by 1 and by number itself. 37 just have two factors 1 and 37. So it is a prime number.


(d) 26


26 = 1 × 26


26 = 13 × 2


26 = 2 × 13


26 = 26 × 1


It has four factors 1, 2, 13 and 26,


So, it’s not a prime number it is a composite number.


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