category name help

In the code example below, I have a line –

wp_list_pages(“title_li=”.$post->post_parent.” etc…

The var $post->post_parent returns a category number. How do I get it to return the category name?

Thanks!

<?php
			if($post->post_parent) {
				$children = wp_list_pages("title_li=".$post->post_parent."&child_of=".$post->post_parent."&echo=0");
			} else {
				$children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");
			}
			if ($children) { ?>
				$cat = $post->post_parent;
				<ul>
				<?php echo $children; ?>
				</ul>
			<?php } ?>