This is the 5181st most frequent Russian word.
немедленному
"Немедленному" means "immediate" or "prompt" in English.
The word 'немедленному' is used in its dative form to describe an immediate necessity for action (action being the subject that requires immediacy).
Мы призываем к немедленному действию.
We call for immediate action.
Here, 'немедленному' is in its dative form, emphasizing the need for an immediate resolution (resolution of the problem, which needs immediacy).
Подход к немедленному решению проблемы был найден.
The approach to the immediate resolution of the problem was found.
In this example, 'немедленному' again appears in its dative form, denoting immediacy in completion (completion being the subject related to immediate action).