  We study the ring of arithmetical functions with unitary convolution, giving
an isomorphism to a generalized power series ring on infinitely many variables,
similar to the isomorphism of Cashwell-Everett between the ring of arithmetical
functions with Dirichlet convolution and the power series ring on countably
many variables. We topologize it with respect to a natural norm, and shove that
all ideals are quasi-finite. Some elementary results on factorization into
atoms are obtained. We prove the existence of an abundance of non-associate
regular non-units.
