更改特定页面的标题?

I need help with something..
I have the following function to display the title for the comments section.

<?php comment_form(); ?>

If I change it to the following:
<?php comment_form(array('title_reply' => 'Comment with image' )); ?> I get the title I want.
But I only want this for page(2123).. How can I do that?

If by page 2123 you mean page id, than

<?php if(get_the_ID() == 2123) comment_form(array('title_reply' => 'Comment with image' )); ?>

should do the job. This should be called inside the loop.