The Math Learning Center has lots of great resources for students, including interactive math tools to help students practise skills with virtual manipulatives. This would work great on a touch screen or tablet.
This is another mobile and web app from the same company and it is perfect for helping students model their thinking as they explore different operations.
Maths Prodigy is a free, interactive game-based resource that is very popular with Irish schools. Pupils have to answers Maths problems to be able to progress in the game. This is a very comprehensive site, with options for personalisation and class reports. Prodigy will work on the web or via tablets.
Other free options for Maths
Khan Academy has high quality resources. Also check out the Khan Academy Kids app for iOS https://www.khanacademy.org/
TopMarks is popular with many Irish teachers: https://www.topmarks.co.uk It has both English and Maths challenges and will work on the web or on tablets.