Numbers and functions in quantum field theory

We review recent results in the theory of numbers and single-valued functions on the complex plane which arise in quantum field theory. These results are the basis for a new approach to high-loop-order calculations. As concrete examples, we provide scheme-independent counterterms of primitive log-divergent graphs in phi(4) theory up to eight loops and the renormalization functions beta, gamma, gamma(m) of dimensionally regularized phi(4) theory in the minimal subtraction scheme up to seven loops.