add code to header on specfic page

functiopns.php

function add_after_head() {
if ( is_page('231') ) {
    ?>
        <!-- Google Tag Manager -->
        <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
                new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
                j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
                'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
            })(window,document,'script','dataLayer','GTM-XXXX');</script>
        <!-- End Google Tag Manager -->
	<?php
  }
}
add_action( 'wp_head', 'add_after_head' );