Write a program to check the given number is a prime number or not?

A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number.

For example, 5 is prime, as only 1 and 5 divide it, whereas 6 is composite, since it has the divisors 2 and 3 in addition to 1 and 6.

The fundamental theorem of arithmetic establishes the central role of primes in number theory: any integer greater than 1 can be expressed as a product of primes that is unique up to ordering. This theorem requires excluding 1 as a prime.

Kotlin program

fun isPrimeNumber(number: Int): Boolean {

    for (i in 2..number / 2) {
        if (number % i == 0) {
            return false
    return true

fun main(a: Array<String>) {
    println("Is 17 prime number? " + isPrimeNumber(17))
    println("Is 19 prime number? " + isPrimeNumber(19))
    println("Is 15 prime number? " + isPrimeNumber(15))


Is 17 prime number? true
Is 19 prime number? true
Is 15 prime number? false

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