Save_Post change Custom Post Type Post title to post id number

A very easy way to accomplish this would be to add something like this into your themes functions.php file:

function update_post(int $id, \WP_Post $post, bool $update) 
{
  // Case the post object to an array
  $data = (array) $post;
  // Set the title to the ID of the post
  $data['post_title'] = $id;
  // We need to remove the action to prevent an infinite loop
  remove_action('save_post', 'update_post');
  wp_update_post($data);
  // Finally re-add the action hook
  add_action('save_post', 'update_post', 10, 3);
}
add_action('save_post', 'update_post', 10, 3);

Notice that you can narrow down which post types to handle by using add_action('save_post_{$post->post_type}', 'update_post', 10, 3);.
So if you custom post type is called video then you would add the hook like this:

add_action('save_post_video', 'update_post', 10, 3);

Read more in the documentation:

• save_post().
• save_post_{$post->post_type}.