Prime Numbers

IMPORTANT

Prime Numbers: Overview

This topic covers concepts such as Prime Numbers, Prime Factorization, Test for a Number to be Prime, Twin Primes, Fundamental Theorem of Arithmetic, Euclidean Theorem, and Sophie Germain Identity.

Important Questions on Prime Numbers

EASY
IMPORTANT

If x, y and z are distinct prime numbers, then their LCM is _______

HARD
IMPORTANT

Prove that n4+4n is a composite number for all n,n>1.

MEDIUM
IMPORTANT

Prove that there are infinitely many primes.

MEDIUM
IMPORTANT

Two prime numbers A, B(A<B) are called twin primes if they differ by 2 (e.g. 11,13, or 41, 43, ....)  If A and B are twin primes with B>23, then what is the largest number that would always divide A+B ?

MEDIUM
IMPORTANT

A and B are playing mathematical puzzles. A asks B "find the number of whole numbers, greater than one, which can divide all the nine three-digit numbers 111, 222, 333, 444, 555, 666, 777, 888 and 999.B immediately gave the desired answer. What it was ?

MEDIUM
IMPORTANT

What is the maximum possible value of n for which 2013 can be written as a sum of n consecutive positive integers ?

EASY
IMPORTANT

By which smallest number we should divide 198396198, to get a perfect square ?

HARD
IMPORTANT

p, q and r are three prime numbers satisfying the relation p + q = r and p < q. What is the value of p?

MEDIUM
IMPORTANT

a and b are twin prime numbers satisfy the condition (6K±1) and another prime number c satisfy the condition (8K+1). Find the least value of a prime number p which satisfy the condition a2+b2=c2+p2 and K is a natural number.

EASY
IMPORTANT

A prime number p is called special if there exist primes p1, p2, p3, p4 such that p=p1+p2=p3-p4.
The number of special primes is
 

EASY
IMPORTANT

A two-digit number ab¯ is called almost prime if one obtains a two-digit prime number by changing at most one of its digits a & b. (For example, 18 is an almost prime number because 13 is a prime number). Then the number of almost prime two-digit numbers is

MEDIUM
IMPORTANT

Find out the prime factors of 28.

MEDIUM
IMPORTANT

Find out the prime factors for 49.

EASY
IMPORTANT

Find the number which is a prime number.

MEDIUM
IMPORTANT

What is prime factorization?

MEDIUM
IMPORTANT

Express each number as the product of its prime factors. Use repeated division method.

117

HARD
IMPORTANT

Express each number as the product of its prime factors. Use repeated division method.

256

MEDIUM
IMPORTANT

Express each number as the product of its prime factors. Use repeated division method.

42

MEDIUM
IMPORTANT

Express each number as the product of its prime factors. Use repeated division method.

150

MEDIUM
IMPORTANT

Express each number as the product of its prime factors. Use repeated division method.

112