const h = 400

​

function setup() {

  createCanvas(w, h);

}

​

function isPrime(n){

  let p = true

  for (let d = 2;d<=Math.floor(Math.sqrt(n));d++){

    if (n%d==0){p = !p;break}

  }

  return p

  }

​

​

function draw() {

  background(220);

  n=20

  let p =isPrime(n)

  if (p==true){text(''+n,w/2,h/2)}

}