  We solve the quantum-mechanical antiferromagnetic Heisenberg model with spins
positioned on vertices of the truncated icosahedron using the density-matrix
renormalization group (DMRG). This describes magnetic properties of the undoped
C$_{60}$ fullerene at half filling in the limit of strong on-site interaction
$U$. We calculate the ground state and correlation functions for all possible
distances, the lowest singlet and triplet excited states, as well as
thermodynamic properties, namely the specific heat and spin susceptibility.
  We find that unlike the exactly solvable C$_{20}$ to C$_{32}$, the lowest
excited state is a triplet rather than a singlet, indicating a reduced
frustration due to the presence of many hexagon faces and the separation of the
pentagon faces. This implies that frustration may be tuneable within the
fullerenes by changing their size.
  The spin-spin correlations are much stronger along the hexagon bonds and
rapidly decrease with distance, so that the molecule is large enough not to be
correlated across its whole extent. The specific heat shows a high-temperature
peak and a low-temperature shoulder reminiscent of the Kagom\'e lattice, while
the spin susceptibility shows a single broad peak and is very close to the one
of C$_{20}$.
