Showing posts with label relatively prime numbers. Show all posts
Showing posts with label relatively prime numbers. Show all posts

Friday, June 15, 2012

Prime Numbers

Prime numbers are positive whole numbers which are divisible by number 1 and itself.  Prime numbers have only two factors. The smallest prime number is 2. Now the question arises is 1 a prime number? No, 1 is not a prime number. So our next question will be why 1 is not a prime number? As per the definition of prime numbers, a prime number must have two factors but 1 only has one factor. It is the only positive integer with exactly one positive divisor.  Therefore it is not considered as a prime number.

Is 2 a prime number? 2 is a prime number as it is divisible by 1 and itself. It has two factors and as per the definition of a prime number, prime number must have two factors. Therefore, 2 is considered as a prime number and it is the only even number which is considered as prime. The other prime numbers are divisible by 2 also so they do not come under a category of a prime number.

Euclid proved that there are infinite prime numbers and there is always a prime greater than the largest known prime number. Many mathematicians tried finding out the largest prime number. The largest prime number found in 2008 was 2^43112609-1

Let us learn about relatively prime numbers. Two numbers that have only 1 as a common factor are called relatively prime numbers. Thus, any two prime numbers are relatively prime numbers. They are also called co prime numbers. However, composite numbers may also be co - prime to each other.

For example: - Numbers 3375 and 2744 are considered as relatively prime because:-
3375 = 1 X 3 X 3 X 3 X 5 X 5 X5
2744 = 1 X 2 X 2 X 2 X 7 X 7 X 7
3375 and 2744 have just 1 as a common factor so they are considered as relatively prime numbers.