Print all unique combination of factors of a given number

Question

What is the most efficient algorithm to print all unique combinations of factors of a positive integer. For example if the given number is 24 then the output should be

Answer 1

bool isprime(int n){
for(int i=2; i<=sqrt(n); i++)
    if(n%i==0)
        return false;
return true;
}

void printprime(int n){

int i,j,y=n;

while(y%2==0){
    cout<<"2 * ";
    y/=2;
}

for(i=3; i<=sqrt(y); i+=2){
    while(y%i==0){
        cout<2)
    cout< done;

for(i=2; i