prop_object_is_number
if (! prop_object_is_number(opn))
if (! prop_object_is_number(pn))
if (! prop_object_is_number(pn))
if (! prop_object_is_number(pn))
if (! prop_object_is_number(pn)) \
if (!prop_object_is_number(num1) || !prop_object_is_number(num2))
if (! prop_object_is_number(pn))
if (! prop_object_is_number(pn))