''I implored Hashem'' [Va'eschanan 3:23]
The Midrash states that Moshe offered 515 prayers to Hashem in order to be allowed to enter the Land of Israel. This is alluded to in the word ''Va'eschanan'' whose numerical value is 515.
Not only does the word ''Va'eschanan'' equal 515, noted the Chasam Sofer [R' Moshe Sofer], but so does the word ''tefillah'' [prayer].
Furthermore, if we add 26 - the numerical value of the ineffable Name of Hashem [yud, hei, vav, hei] to the number 515, we will get 541 - the numerical value of the word Yisrael.
Also see: What Happens to Unanswered Prayers