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is_prime.js
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is_prime.js
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function isPrime(number) {
// Prime numbers must be greater than 1
if (number <= 1) {
return false;
}
// 2 and 3 are prime numbers
if (number <= 3) {
return true;
}
// If the number is divisible by 2 or 3, it's not prime
if (number % 2 === 0 || number % 3 === 0) {
return false;
}
// Check for prime using 6k +/- 1 rule
// All prime numbers (except 2 and 3) can be expressed as 6k ± 1.
for (let i = 5; i * i <= number; i += 6) {
if (number % i === 0 || number % (i + 2) === 0) {
return false;
}
}
return true;
}
// Example usage:
console.log(isPrime(5)); // Output will be true (5 is a prime number)
console.log(isPrime(12)); // Output will be false (12 is not a prime number)
console.log(isPrime(29)); // Output will be true (29 is a prime number)