function bp_is_root_blog( $blog_id = 0 ) {

	// Assume false.
	$is_root_blog = false;

	// Use current blog if no ID is passed.
	if ( empty( $blog_id ) || ! is_int( $blog_id ) ) {
		$blog_id = get_current_blog_id();
	}

	// Compare to root blog ID.
	if ( bp_get_root_blog_id() === $blog_id ) {
		$is_root_blog = true;
	}

	/**
	 * Filters whether or not we're on the root blog.
	 *
	 * @since 1.5.0
	 *
	 * @param bool $is_root_blog Whether or not we're on the root blog.
	 */
	return (bool) apply_filters( 'bp_is_root_blog', (bool) $is_root_blog );
}