My Son has a special interest on Alphabets and spellings over Numbers. Infact he learnt Alphabets both upper case and lower case with the help of Ipad Apps only. After he learnt to identify the Alphabets just as a variation I gave him this First words Professional app by Learning Touch LLC. He totally enjoyed the app and learnt some spelling of objects, Animals and birds etc.
First Words Professional is an paid app (Rs.620) which has categories like Animals, At home, Colour etc. This app can be downloaded through the following link(for IOS)
Through the settings parents can choose varios options according to the childs level of understanding.
Following is a video of how much son plays and enjoys the app.
He even learnt to write some of the words he learnt through this app. Following is the video of how he practices the learnt three letter words.