How To Use A Prime Number

By Author: Pierce Brosnan
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Introduction to Prime Number

A prime number is a natural number which has only 1 and the number itself as factors. For example, 2, 3, 5, 7, 11, 13, etc. are all prime numbers. Composite number is a natural number which has factors other than just 1 and the number itself. For example, 4, 6, 8, 9, 10, 12, etc. are all composite numbers. By convention, the number 1 is not prime or composite number.

Properties of Prime Number

a) 2 is the only even prime number and also lowest even prime number.

b) 3 is the lowest odd prime number.

c) Between 1 and 100 prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97. Between numbers 1 to 100 there are 25 prime numbers.

d) In negative numbers there are no prime numbers.

Prime Number - Identification

Example 1: Check whether the number 3431 is prime or not.

Solution:

Step 1: Find the square root of 3431. The Square root of 3431 is 58.57......

Step 2: If the result of square root is an integer it is automatically composite number.

Step ...
... 3: If number ends with 0, 2, 4, 5, 6, 8. Then that is not prime number. 3431 ends in a 1, so go to next step

Step 4: Find the sum of digits of number, if the sum is divisible by 3, given number is composite number -> 3 + 4 + 3 + 1= 11. 11 is not divisible by 3.

step 5: Divide the given number by all the prime numbers less than the square root. Note: you can skip 2, 3, and 5.

Since the square root of 3431 is 58.57... Divide 3431 by primes less than 58

(7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53).

Since 3431 is divisible by 47, it is not prime number and therefore composite number.

Step 6: If a given number is not divisible by any of the prime numbers less than the square root, it is prime number otherwise it is composite number.

Example 2: Check whether the number 2657 is prime or not.

Solution:

Step 1: Find the square root of 2657. The Square root of 2657 is 51.54......

Step 2: If the result of square root is an integer it is automatically composite number.

Step 3: If number ends with 0, 2, 4, 5, 6, 8. Then that is not prime number. 2657 ends in a 7, so go to next step

Step 4: Find the sum of digits of number, if the sum is divisible by 3, given number is composite number -> 2 + 6 + 5 + 7= 20. 20 is not divisible by 3.

Step 5: Divide the given number by all the prime numbers less than the square root. Note: you can skip 2, 3, and 5.

Since the square root of 2657 is 51.54... Divide 2657 by primes less than 51

(7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47).

Since 2657 is not divisible by any of those number, it is prime number and therefore not composite number.

Comprehend more on about rational irrational numbers and its Circumstances. Between, if you have problem on these topics The normal distribution Please share your views here by commenting.