Is a fantastic book for a kid who is very interested in math, but not yet reading. Basically it depicts the prime factors of the numbers 1 to 100 with very clever pictures. It was the favorite book of my son when he was about 4.5, and we still call prime factors monsters internally (eg, reducing fractions involves "monster battles" and so forth).

http://www.amazon.com/Count-Monsters-Richard-Evan-Schwartz/dp/1568815786

Thanks for the recommendation. I have a 4.5 year old who loves math.

Any other book recommendations for the math-minded preschooler?

We've read:
Apple Fractions
G is for Google (parts of it)
On Beyond a Million
Millions to Measure