I need help in order to create a program using the dart language to print all divisors of a( 2^63 - 1) number in crescent order

Question

hope everyone is good. I'm a student and I'm having a really bad time with a homework. My teacher asked me to create a program to print every divisor of a number in crescent order in less than 10 seconds using the dart language. The problem is: He wants the divisor to be a number of about 14 characters, more precisely the number: 21,001,713,200,000. I'm having overflow issues because this is a large number. I really appreciate if someone could help me.

`

void main(){
    int a = 40;
    int aux = 0;
    for (int i = 2; i < a; i++) {
        if (a % i == 0) {
            ++aux;
        }
    }
    List<int> diva = [];
    int k = 0;
    aux = 1;
    for (int i = 0; i < a; i++) {
        ++aux;
        if (a % aux == 0) {
            diva.insert(k++, aux);
        }
    }
  print('${diva}');
}

`