Mathematics · Quantitative Aptitude

Number Theory

438 Questions

Number theory explores the properties and relationships of integers, focusing heavily on prime and composite numbers. Key areas include identifying prime numbers, understanding co primes, and exploring mathematical conjectures like Goldbach's. These questions are a core component of quantitative aptitude sections in banking and government exams.

Prime number identificationCo prime propertiesGoldbach conjectureOdd and even numbersDivisibility rules

Number Theory Questions

Multiple choice

Which of the following cannot be written as the sum of two prime numbers?

  1. 16

  2. 21

  3. 23

  4. 24

  5. 30
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Is the correct option. 23 = 2 + 21...............(21 is not prime) = 3 + 20..............(20 is not prime) = 5 + 18..............(18 is not prime) = 7 + 16..............(16 is not prime) = 11 + 12............(12 is not prime) = 13 + 10............(10 is not prime) = 17 + 6..............(6 is not prime) = 19 + 4..............(4 is not prime). So, option (3) is correct.

Multiple choice

Which of the following is a prime number?

  1. 143

  2. 131

  3. 147

  4. 161
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

[Explanation: 131 has exactly 2 factors, i.e., 1 and 131 Therefore, It is a prime number. 143 is divisible by 11, 147 is divisible by 7 and 161 is divisible by 7]