ABA is an Elixir library for performing validation and lookups on ABA routing numbers. It stores all routing numbers and bank information in an ETS table. Therefore, you should initialize the application in a supervision tree.

Full docs here: https://hexdocs.pm/aba/index.html

Add aba to your list of dependencies in mix.exs:

def deps do
  [
    {:aba, "~> 0.3"}
  ]
end

To perform routing number validation without an ETS table lookup:

iex> ABA.routing_number_valid?("111900659")
true

Otherwise, performing lookups can be done with

iex> ABA.get_bank("111900659")
{:ok, %ABA.Bank{routing_number: "111900659", name: "WELLS FARGO BANK",
                       address: "255 2ND AVE SOUTH", city: "MINNEAPOLIS",
                       state: "MN", zip: "55479"}}