ABC26GN0120 · Number System

Subject: General Aptitude · Chapter: Number System · Exam: 2010 · Marks: · Difficulty:

Which of the following is not a prime number?

(a)21

(b)23

(c)29

(d)43

Answer

Answer (as printed): A

Explanation

Clearly, $21=3 \times 7$, so 21 is not prime.

Explanation as extracted from the printed page; notation may be imperfect.

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