  B\"uchi arithmetics BA_n, n >= 2, are extensions of Presburger arithmetic
with an unary functional symbol V_n(x) denoting the largest power of n that
divides x. Definability of a set in BA_n is equivalent to its recognizability
by a finite automaton receiving numbers in their n-ary expansion. We show that
B\"uchi arithmetics BA_n and BA_m are bi-interpretable for any n,m.
Furthermore, we establish that any interpretation of some structure in BA_n is
isomorphic to some one-dimensional interpretation; however, this isomorphism
must not be BA_n-definable.
