Arithmetic 21 Foundations 20 Mathematics 3 Set theory 3 Logic, Symbolic and mathematical 2 Number concept 2 Number theory 2 Numbers, Real 2 Philosophy 2 Algebraic logic 1 Equivalence classes (Set theory) 1 Foundation 1 Geometry 1 History 1 Induction (Mathematics) 1 Mathematical analysis 1 Numbers, Natural 1 Study and teaching 1