You can apply it to as many pages as you want, but the conditions need to be ordered properly.
This isn't going to do anything because there isn't an if to start the conditions, or an else to end them:
<?php } else if (is_page('46','49','51','53')) { ?>
If you want to have one page have code A, and then several pages have code B, and all the rest have code C, you want to start with the most specific, a single page, then the more broad, several pages, then the catch-all, like this:
<?php
if ( is_page('37')) {
echo "<p>something for page 37 only goes here</p>";
}
elseif ( is_page('46','49','51','53')) {
echo "<p>something for pages 46, 49, 51, and 53 goes here</p>";
}
else {
echo "<p>something for all other pages goes here</p>";
}
?>
Does that make sense?