Go Language - Program to Check Whether a Number is Prime or Not

• Prime numbers are natural numbers that are only divisible by 1 and the number itself. 
• A prime number cannot be divided by any other numbers without leaving a remainder. 
• An example of a prime number is 17. It can only be divided by 1 and 17, which has only two factors 1 and 5.
• Let's take another example of the number 6, which has more than two factors, i.e 1, 2, 3, and 6. This means 6 is not a prime number.

Example 1. Go Program to check whether the given number is Prime or not

package main

import (
    "fmt"
)

func main() {
    CheckPrimeNumber(11)
    CheckPrimeNumber(1)
    CheckPrimeNumber(23)
    CheckPrimeNumber(20)
    CheckPrimeNumber(-9)
}

func CheckPrimeNumber(number int) {

    isPrime := true

    if number < 0 {
        fmt.Println("Number must be greater than 0")
    } else if number == 0 || number == 1 {
        fmt.Println(number, "is not a  prime number")
    } else {
        for i := 2; i <= number/2; i++ {
            if number%i == 0 {
                fmt.Println(number, " is not a  prime number")
                isPrime = false
                break
            }
        }
        if isPrime == true {
            fmt.Println(number, "is a prime number")
        }
    }
}

Output:

Example 2. Go Program to check whether the number from standard input is Prime or not

package main
import (
    "fmt"
)
func main() {
    var number int
    fmt.Println("Enter an integer value : ")
    _, err := fmt.Scanf("%d", &number)
    if err != nil {
        fmt.Println(err)
    }
    CheckPrimeNumber(number)
}
func CheckPrimeNumber(number int) {
    isPrime := true
    if number < 0 {
        fmt.Println("Number must be greater than 0")
    } else if number == 0 || number == 1 {
        fmt.Println(number, "is not a  prime number")
    } else {
        for i := 2; i <= number/2; i++ {
            if number%i == 0 {
                fmt.Println(number, " is not a  prime number")
                isPrime = false
                break
            }
        }
        if isPrime == true {
            fmt.Println(number, "is a prime number")
        }
    }
}

Output: