https://cosas.wordpress.com/2010/10/25/la-criba-de-sundaram/

https://es.wikibooks.org/wiki/Implementaci%C3%B3n_de_algoritmos_de_teor%C3%ADa_de_n%C3%BAmeros/Criba_de_Erat%C3%B3stenes

http://www.topcoder.com/tc?module=Static&d1=tutorials&d2=primalityTesting

https://stackoverflow.com/questions/2468412/finding-a-prime-number-after-a-given-number/2473188#2473188

#include
using namespace std;

/* This function calculates (ab)%c /
int modulo(int a,int b,int c){
long long x=1,y=a; // long long is taken to avoid overflow of intermediate results
while(b > 0){
if(b%2 == 1){
x=(xy)%c;
}
y = (y*y)%c; // squaring the base
b /= 2;
}
return x%c;
}

/* this function calculates (ab)%c taking into account that ab might overflow /
long long mulmod(long long a,long long b,long long c){
long long x = 0,y=a%c;
while(b > 0){
if(b%2 == 1){
x = (x+y)%c;
}
y = (y2)%c;
b /= 2;
}
return x%c;
}

/* Miller-Rabin primality test, iteration signifies the accuracy of the test */
bool Miller(long long p,int iteration){
if(p<2){
return false;
}
if(p!=2 && p%2==0){
return false;
}
long long s=p-1;
while(s%2==0){
s/=2;
}
for(int i=0;i<iteration;i++){
long long a=rand()%(p-1)+1,temp=s;
long long mod=modulo(a,temp,p);
while(temp!=p-1 && mod!=1 && mod!=p-1){
mod=mulmod(mod,mod,p);
temp *= 2;
}
if(mod!=p-1 && temp%2==0){
return false;
}
}
return true;
}

int main(int argc, char* argv[])
{

int input = 1000;
int i = 0;

if(input%2==0)
    i = input+1;
else i = input;

for(;i<2*input;i+=2) // from Rajendra's answer
    if(Miller(i,20)) // 18-20 iterations are enough for most of the applications.
        break;
cout<<i<<endl;

return 0;

}

https://www.solumaths.com/es/sitio/pagina-principal
http://www.librosmaravillosos.com/eldiablodelosnumeros/
https://www.smartick.es

prime factorization