Question

How to find the sum of all the primes below two million in Node.js

Answer 1

function isPrime(n) {
    if (n < 2 || (n % 2 == 0 && n != 2)) {
        return 0;
    }
  
    const count = Math.floor(Math.sqrt(n));
    for (let i = 3; i <= count; i += 2) {
        if (n % i == 0) {
            return 0;
        }
    }
    return 1;
}
  
let num = 2000000;
let sum = 0;

for (let i = 2; i < num; i++) {
    if (isPrime(i)) {
        sum += i;
    }
}
        
console.log("sum = " + sum);

  
  
  
/*
run:
  
sum = 142913828922

*/

 

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