For math I can recommend you Tiggly Chef Addition, it's a cool free app which gives an opportunity for a child to learn numbers in the form of a cooking game. Numbers are used in it for counting bowls and collecting a recipee for making various dishes :) Pip and The Big Wide World is another good one, it has an adventure storyline and also helps a child to get some knowledge in science too. Bugs and Numbers is nice for leaning numbers and shapes too, it's for 4 yo children but rather simple that's why you can try it in your age too.
And in case of alphabet The Amazing Alphabet Match-Up, Alphabet Antics, Zebrainy ABC Wonderlands Zebrainy ABC Wonderlands Game on the AppStore
, Duck's Alphabet and ABCya! are considered as the best ones. All of them are really effective for learning, have good quality and nice graphics.
Hope that was helpful!