diff --git a/lib/koans/04_numbers.ex b/lib/koans/04_numbers.ex
new file mode 100644
index 0000000..89d4bb9
--- /dev/null
+++ b/lib/koans/04_numbers.ex
@@ -0,0 +1,92 @@
+defmodule Numbers do
+  require Integer
+  use Koans
+
+  @intro "Why is the number six so scared? Because seven eight nine!\nWe should get to know numbers a bit more!"
+
+  koan "Are you odd?" do
+    assert Integer.is_odd(3) == ___
+  end
+
+  koan "Actually you might be even" do
+    assert Integer.is_even(4) == ___
+  end
+
+  koan "Let's grab the individual digits in a list" do 
+    individual_digits = Integer.digits(58127)
+    assert individual_digits == ___
+  end
+
+  koan "Oh no! I need it back together" do 
+    number = Integer.undigits([1, 2, 3, 4])
+
+    assert number == ___
+  end
+
+  koan "I think I need my number as a char" do 
+    char_digit = Integer.to_char_list(7)
+
+    assert char_digit == ___
+  end
+
+  koan "Actually I want my number as a string" do 
+    string_digit = Integer.to_string(1234)
+
+    assert string_digit == ___
+  end
+
+  koan "The meaning of life in hexidecimal is 2A!" do
+    assert Integer.parse("2A", 16) == {___, ""}
+  end
+
+  koan "I don't want this decimal point, let's round up" do
+    assert Float.ceil(34.25) == ___
+  end
+
+  koan "OK, I only want it to 1 decimal place" do
+    assert Float.ceil(34.25, 1) == ___
+  end
+
+  koan "Rounding down is what I need" do
+    assert Float.floor(99.99) == ___
+  end
+
+  koan "Rounding down to 2 decimal places" do
+    assert Float.floor(12.345, 2) == ___
+  end
+
+  koan "Just want to parse to a float" do
+    assert Float.parse("34.5") == {___, ""}
+  end
+
+  koan "Hmm, I want to parse this but it has some strings" do
+    assert Float.parse("1 million dollars") == {___, " million dollars"}
+  end
+
+  koan "Round the number up or down for me" do
+    assert Float.round(5.5) == ___
+    assert Float.round(5.4) == ___
+    assert Float.round(8.94, 1) == ___
+    assert Float.round(-5.5674, 3) == ___
+  end
+
+  koan "I want the first and last in the range" do
+    first..last = Range.new(1, 10)
+
+    assert first == ___
+    assert last == ___
+  end
+
+  koan "Does my number exist in the range?" do
+    range = Range.new(1, 10)
+
+    assert 4 in range == ___
+    assert 10 in range == ___
+    assert 0 in range == ___
+  end
+
+  koan "Is this a range?" do    
+    assert Range.range?(1..10) == ___
+    assert Range.range?(0) == ___
+  end
+end
\ No newline at end of file
diff --git a/lib/koans/04_atoms.ex b/lib/koans/05_atoms.ex
similarity index 100%
rename from lib/koans/04_atoms.ex
rename to lib/koans/05_atoms.ex
diff --git a/lib/koans/05_tuples.ex b/lib/koans/06_tuples.ex
similarity index 100%
rename from lib/koans/05_tuples.ex
rename to lib/koans/06_tuples.ex
diff --git a/lib/koans/06_lists.ex b/lib/koans/07_lists.ex
similarity index 100%
rename from lib/koans/06_lists.ex
rename to lib/koans/07_lists.ex
diff --git a/lib/koans/07_keyword_lists.ex b/lib/koans/08_keyword_lists.ex
similarity index 100%
rename from lib/koans/07_keyword_lists.ex
rename to lib/koans/08_keyword_lists.ex
diff --git a/lib/koans/08_maps.ex b/lib/koans/09_maps.ex
similarity index 100%
rename from lib/koans/08_maps.ex
rename to lib/koans/09_maps.ex
diff --git a/lib/koans/09_structs.ex b/lib/koans/10_structs.ex
similarity index 100%
rename from lib/koans/09_structs.ex
rename to lib/koans/10_structs.ex
diff --git a/lib/koans/10_pattern_matching.ex b/lib/koans/11_pattern_matching.ex
similarity index 100%
rename from lib/koans/10_pattern_matching.ex
rename to lib/koans/11_pattern_matching.ex
diff --git a/lib/koans/11_functions.ex b/lib/koans/12_functions.ex
similarity index 100%
rename from lib/koans/11_functions.ex
rename to lib/koans/12_functions.ex
diff --git a/lib/koans/12_enums.ex b/lib/koans/13_enums.ex
similarity index 100%
rename from lib/koans/12_enums.ex
rename to lib/koans/13_enums.ex
diff --git a/lib/koans/13_processes.ex b/lib/koans/14_processes.ex
similarity index 100%
rename from lib/koans/13_processes.ex
rename to lib/koans/14_processes.ex
diff --git a/lib/koans/14_tasks.ex b/lib/koans/15_tasks.ex
similarity index 100%
rename from lib/koans/14_tasks.ex
rename to lib/koans/15_tasks.ex
diff --git a/lib/koans/15_agents.ex b/lib/koans/16_agents.ex
similarity index 100%
rename from lib/koans/15_agents.ex
rename to lib/koans/16_agents.ex
diff --git a/lib/runner.ex b/lib/runner.ex
index 98cc08b..9741bb4 100644
--- a/lib/runner.ex
+++ b/lib/runner.ex
@@ -3,6 +3,7 @@ defmodule Runner do
     Equalities,
     Strings,
     Sigils,
+    Numbers,
     Atoms,
     Tuples,
     Lists,
diff --git a/test/koans/numbers_koans_test.exs b/test/koans/numbers_koans_test.exs
new file mode 100644
index 0000000..f60690e
--- /dev/null
+++ b/test/koans/numbers_koans_test.exs
@@ -0,0 +1,28 @@
+defmodule NumbersTests do
+  use ExUnit.Case
+  import TestHarness
+
+  test "Numbers" do
+    answers = [
+      true,
+      true,
+      [5, 8, 1, 2, 7],
+      1234,
+      '7',
+      "1234",
+      42,
+      35.0,
+      34.3,
+      99.0,
+      12.34,
+      34.5,
+      1.0,
+      {:multiple, [6.0, 5.0, 8.9, -5.567]},
+      {:multiple, [1, 10]},
+      {:multiple, [true, true, false]},
+      {:multiple, [true, false]},
+    ]
+
+    test_all(Numbers, answers)
+  end
+end