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Standard arithmetic with +, -, *. Division is more nuanced: / always returns a float; div is integer division; rem is the remainder.

IO.puts 7 + 3       # 10
IO.puts 7 * 3       # 21
IO.puts 7 / 3       # 2.3333... (always float)
IO.puts div(7, 3)   # 2
IO.puts rem(7, 3)   # 1
IO.puts :math.pow(2, 10)   # 1024.0 (Erlang module)

Integers are arbitrary precision — 1 |> Stream.iterate(&(&1 * 2)) |> Enum.at(1000) works without overflow.

For more math, the :math module (from Erlang) provides :math.sqrt, :math.log, etc. Note the leading colon — that's how you call modules whose names are atoms (Erlang modules).