strip_tags in get_the content

$content = get_the_content();
// regex (fixed) replacing '<embed>' with '(embed )'
$content = preg_replace("/<embed?[^>]+>/i", "(embed) ", $content);
// remove all tags
$content = wp_strip_all_tags($content);
echo $content;

Edited according to the first comment:

What you are trying to remove are not tags, these are HTML character entities. E. g., <p> was converted to <p> by WordPress when you’ve saved the content in the visual editor.

You have two choices:

1. edit the content in the built-in text editor to remove those entities (switch the editor from Visual to HTML mode);
2. use different regexes to remove entities after the post was fetched.

For example (not tested, but you have the idea):

$content = preg_replace("/<embed?[.]+&gt/i", "(embed) ", $content);
$content = preg_replace("/<[.]+&gt/i", "", $content);