Euler

I'm working on Euler problem number 12. I've got the following:

//cut out my includes
bool IsPrime(int num)
{
    bool prime = true;
    int number2 =(int) floor (sqrt ((long double)num));
    for ( int j = 2; j <= number2; j++){
        if ( num!=j && num % j == 0 ){     
            prime = false;
            break;
        }
    }
    return prime;
}

int NumDivisors(__int64 num)
{
    int count = 0;
    if(!IsPrime(num))
    {
        __int64 number2 = num/2;
        for ( __int64 j = 2; j <= number2; j++){
            if ( num % j == 0 ){     
                count++;
            }
        }
    }
    return count;
}

int _tmain(int argc, _TCHAR* argv[])
{
    bool found = false;
    __int64 num = 1;
    __int64 maxdiv = 0;
    while(!found)
    {
        __int64 trinum = 0;
        for(int i = 0;i<=num;++i) trinum += i;
        int div = NumDivisors(trinum);
        if(div>maxdiv) maxdiv = div;
        if(div>500) found = true;
        if(!found) ++num;
    }
    return 0;
}
The problem is, NumDivisors is horribly inefficient. I mean 30 minutes at 2.5ghz and I'm only on num=9219 with a maxdiv of 478. Any suggestions?

>>6
Tgirl here, we're not microsoft