Function that contains alert of random number on button click - Javascript

I have this code to try and make an alert pop up on the web page that says "your number is" + "(1-25)". Nothing happens when I press the button. Does math.random only produce a number to the console or why does this not work. Here is my code.

function rGen () {
 let rNum = (Math.floor(Math.random() * 25))
 alert(rNum + "is your number")
}


let button1 = document.getElementById('button1');
button1.addEventListener('click' rGen)