How can i found the application id of my heroku application?

I have an ember project deployed on heroku and also an api to make graphs calculation. I have to set an appid to my api application, and i can't figure out where to find it. The api is a parse-server api, which is deployed on heroku.

if (environment === 'production') {
    ENV.APP.HOST = 'xxxxxx(my url).herokuapp.com'
    ENV.rootURL = null;
    ENV.locationType = 'hash';
    ENV.APP.applicationId = '(I don't know what to set here)'
  }

That's my code on environment.js