In this paper,Kaplansky-type theorems are given to characterize GCD-monoids and valuation monoids.Also,(unique) r-factorable monoids are defined and it is shown that S is a Krull monoid if and only if S is a unique t-factorable (resp.,w-factorable)monoid if and only if S is a t-factorable (resp.,w-factorable) t-Pr(u)fer monoid.