Shubham Borkar

Davneet Singh
Expert

Hello Shubham,

Prime numbers are those numbers which are divisible by only 1 and itself.

For example - 2 is a prime number.

From 1 to 100, prime numbers are

Let's check how we find if 53 is a prime number. Let n = 53

We follow the following steps to check if a number is prime or not

Step | Description | Example |
---|---|---|

1 | Is n a positive whole number >= 2? If not, n is 1, or 0, or some negative number, or decimal number. None of these are prime. If n is a whole number >=2, continue to the next step. | 53 is a positive whole number >= 2, so continue to the next step. |

2 | Does n = 2? If so, it is prime. If not, continue to the next step. | 53 does not equal 2, so continue to the next step. |

3 | Is n an even number? If so, it is not prime, because 2 is the only even prime number and we eliminated 2 in the previous step. If n is not even, continue. | 53 is not an even number, so continue to the next step. |

4 | Is n = 5? If so, n is prime. If not, continue to the next step. | 53 does not equal 5, so continue. |

5 | Is n a multiple of 5; that is, is the digit in its ones' place 0 or 5? If so, n is not prime. If n is not a multiple of 5, continue to the next step. | 53 is not a multiple of 5, so continue. |

6 | Is n = 3? If so, n is prime. If not, continue to the next step. | 53 does not equal 3, so continue. |

7 | Divide n by 3. If you get a remainder, continue to the next step. If n divided by 3 results in no remainder, then n is not prime. | 53 divided by 3 = 17 with a remainder of 2, so continue. |

8 | Is n = 7? If so, n is prime. If not, continue to the next step. | 53 does not equal 7, so continue. |

9 | Divide n by 7. If you get a remainder, n is prime. If n divided by 7 leaves no remainder, n is not prime. |
53 divided by 7 = 7 with a remainder of 4; therefore 53 is a prime number. Its only factors are itself and 1. |

Source: http://www.scsb.org/trh/prime/

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