Спасибо за ответ, написала прямой запрос к БД, он работает, предложеннные варианты не проверяла.
[CODE] global $DB;
$strSql = '
SEL ECT MAX(CAST(VALUE AS UNSIGNED)) AS max_num
FR OM b_iblock_element_property AS a
INNER JOIN b_iblock_property AS b ON b.ID = a.IBLOCK_PROPERTY_ID
WHERE b.CODE = "NUMBER"
';
$NumberPubl = $DB->Query($strSql)->getNext();
$NumberPubl = $NumberPubl['max_num'] ;
[/CODE]
[CODE] global $DB;
$strSql = '
SEL ECT MAX(CAST(VALUE AS UNSIGNED)) AS max_num
FR OM b_iblock_element_property AS a
INNER JOIN b_iblock_property AS b ON b.ID = a.IBLOCK_PROPERTY_ID
WHERE b.CODE = "NUMBER"
';
$NumberPubl = $DB->Query($strSql)->getNext();
$NumberPubl = $NumberPubl['max_num'] ;
[/CODE]