Which of the following is not a prime number?1, 7, 11, 13
Explanation
Answer A: A prime number is a number which is exactly divisible only by itself and 1. Example: 7, 11, 13 etc. Number 7 is not exactly divisible by any number other than 1 and 7. One (1) is not a prime number. The number 1 has only one factor and is not considered to be a prime number
Key takeaway: A prime number is a number which is exactly divisible by itself and 1 only. It is not exactly divisible by any other number. In GMAT questions based on prime numbers are commonly asked. It is useful to remember the first 15 Prime numbers 2,3,5,7,11,13,17,19,23,29,31,37,41, 43 and 47.
