Consider the series: 2, 3, 5, 7, 11, 13, 17, 19, 21, 23, 29
Find the number which is different from other similar numbers.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 21
The series lists the prime numbers in order: numbers with no factor other than 1 and themselves.
Option (1) 29 — prime.
Option (2) 23 — prime.
Option (3) 19 — prime.
Option (4) 21 — \(21=3\times7\), so it is not a prime; 21 is the odd one out.