Random Number doesn't print the result

I'm trying to get a random number when cliking a button and I'm doing something wrong, it works with another example that doesn't have a function so I must be doing something wrong but can't find what. Right now it prints the function code as text.

This is the html:

<div id="aleatori">
   <button v-on:click="randomNumber">Aleatori</button>
   <p></p>
</div>

This is the js

var aleatori = new Vue({
    el:'#aleatori',
    data: {
        randomNumber: function () {
            this.random = Math.floor(Math.random() * (10 - 1 + 1)) + 1
          }
    }
})