035.js

// The number, 197, is called a circular prime because all rotations of the 
// digits: 197, 971, and 719, are themselves prime.

// There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 
// 71, 73, 79, and 97.

// How many circular primes are there below one million?

function isPrime(n) {
    if (n < 2) return false;
    var q = Math.floor(Math.sqrt(n));
    for (var i = 2; i <= q; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

function isCircularPrime(n) {
    if (!isPrime(n)) {
        return false;
    }
    var str = n.toString();
    var len = str.length;
    while (len--) {
        if (!isPrime( parseInt(str.substring(len) + str.substring(0, len), 10) )) {
            return false;
        }
    }
    return true;
}

function countCirculars(max) {
    var cnt = 0;
    if (max >= 2) {
        cnt++;// '2' is a circular prime
    }
    for (var i = 3; i < max; i += 2) {
        if (isCircularPrime(i)) {
            cnt++;
        }
    }
    return cnt;
}

console.log( countCirculars(1000000) );