  We give a representation of the parity-even part of the planar two-loop
six-gluon MHV amplitude of N=4 super-Yang-Mills theory, in terms of
loop-momentum integrals with simple dual conformal properties. We evaluate the
integrals numerically in order to test directly the ABDK/BDS all-loop ansatz
for planar MHV amplitudes. We find that the ansatz requires an additive
remainder function, in accord with previous indications from strong-coupling
and Regge limits. The planar six-gluon amplitude can also be compared with the
hexagonal Wilson loop computed by Drummond, Henn, Korchemsky and Sokatchev in
arXiv:0803.1466 [hep-th]. After accounting for differing singularities and
other constants independent of the kinematics, we find that the Wilson loop and
MHV-amplitude remainders are identical, to within our numerical precision. This
result provides non-trivial confirmation of a proposed n-point equivalence
between Wilson loops and planar MHV amplitudes, and suggests that an additional
mechanism besides dual conformal symmetry fixes their form at six points and
beyond.
