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 is the only prime number that is the sum of four consecutive prime numbers?

  1. 11

  2. 13

  3. 17

  4. 23
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

17 is the sum of four consecutive prime numbers: 2 + 3 + 5 + 7 = 17. These are the first four prime numbers. Checking other options: 11 is not the sum of four consecutive primes, 13 is not (3 + 5 + 7 + 11 = 26), and 23 is not either. 17 holds this unique property. This is a specific number theory fact about prime numbers.

Multiple choice

Which of the following numbers is not co-prime with 14?

  1. 11

  2. 13

  3. 15

  4. 7

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

HCF of 11 and 14 is 1, hence 11 is co-prime with 14. HCF of 13 and 14 is 1, hence 13 is co-prime with 14. HCF of 15 and 14 is 1, hence 15 is co-prime with 14. HCF of 7 and 14 is 7, hence 7 is not co-prime with 14.