Magento Display Product SKU

If you happen to use Magento to develop your e-commerce site, and want to display SKU number on your product page, here is how you can use the magic method getSku to do it. On your app/design/frontend/default/default/template/catalog/product/view.phtml page, add in the line below:

<?php echo 'RN #'.nl2br($_product->getSku()) ?>

Source: http://www.blog.highub.com/cms/magento-display-product-sku/