[Mithadan]

Mhagain, you are correct about my "math," however, 111 years is not long for a Numenorean, perhaps one generation. And much of this time would have been consumed by establishing settlements, growing food and beginning the construction or Arnor and Gondor. Moreover, Sauron did not attack Gondor until 3429. While the Exiles would certainly have reason to establish a defensive militia, until Sauron acted, they would not have needed an army with offensive capabilities.

As Kuruharan discusses persuasively, an army requires logistics and support. More so here because, unlike Sauron's army that is sitting in or near Mordor, the Last Alliance must travel across Eriador and to the south. With Arnor and Gondor in their infancy, even assuming alliances with existing settlements, many Men would need to stay home to feed and support the army.