Question

How to find the 100001 prime number in PHP

Answer 1

function isPrime($num) {
    if ($num < 2) {
        return false;
    }
    
    for ($i = 2; $i <= sqrt($num); $i++) {
        if ($num % $i == 0) {
            return false;
        }
    }
    
    return true;
}

$count = 0;
$number = 1;
$target = 100001;

while ($count < $target) {
    $number++;
    if (isPrime($number)) {
        $count++;
    }
}

echo "The 100,001st prime number is: $number\n";



/*
run:

The 100,001st prime number is: 1299721

*/

 

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