<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Prime Checker</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            text-align: center;
        }

        input {
            width: 200px;
            height: 40px;
            font-size: 20px;
        }

        button {
            width: 100px;
            height: 40px;
            font-size: 20px;
        }

        p {
            font-size: 24px;
            color: green;
        }
    </style>
</head>
<body>
    <h1>Prime Checker</h1>
    <p>Enter a positive number and click the button to check if it is prime or not.</p>
    <input type="number" id="number" min="1" value="1">
    <button id="check">Check</button>
    <p id="result"></p>
    <script>
        // get the input element
        const number = document.getElementById("number");

        // get the button element
        const check = document.getElementById("check");

        // get the result element
        const result = document.getElementById("result");

        // add a click event listener to the button
        check.addEventListener("click", function() {
            // get the input value
            let n = parseInt(number.value);

            // check if the input is valid
            if (isNaN(n) || n < 1) {
                // display an error message
                result.textContent = "Please enter a valid positive number.";
            } else {
                // call the function to check if the number is prime
                let isPrime = checkPrime(n);

                // display the result
                if (isPrime) {
                    result.textContent = n + " is a prime number.";
                } else {
                    result.textContent = n + " is not a prime number.";
                }
            }
        });

        // function to check if a number is prime
        function checkPrime(n) {
            // check if the number is 1
            if (n === 1) {
                // 1 is neither prime nor composite
                return false;
            }

            // check if the number is 2
            if (n === 2) {
                // 2 is the only even prime number
                return true;
            }

            // check if the number is even
            if (n % 2 === 0) {
                // even numbers are not prime
                return false;
            }

            // loop from 3 to the square root of the number
            for (let i = 3; i <= Math.sqrt(n); i += 2) {
                // check if the number is divisible by any odd number
                if (n % i === 0) {
                    // the number is not prime
                    return false;
                }
            }

            // the number is prime
            return true;
        }
    </script>
</body>
</html>

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body{
  padding: 25px;
}
.title {
	color: #228B22;
	font-family: Candara;
}

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HTML-Javascript

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Example

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