I can't say enough good things about this show. Whether it's the visual representation of numbers and the ability to relay the point across to the audience or it catchy songs; Numberblocks is like a math class your kids will want to attend. It's characters are well written with personalities of their own and they show pride in their numerological abilities, for example there is a square club which contains 1, 4, 9, 16, 25 etc.
The show also strongly grasps all 4 of the basic mathematical functions: +-×÷. It explains these in a way that's fun for children and as long as they have at least some interest in math, they should be able to grasp the concepts and do basic math.