diff --git a/numberwords.py b/numberwords.py
index 8c590cd..e7baab9 100644
--- a/numberwords.py
+++ b/numberwords.py
@@ -15,19 +15,46 @@ TENS_NAMES = [
 ]
 
 def int_under_1000000_to_str(number):
-    return "umm..."
+    if number < 1000:
+        return int_under_1000_to_str(number)
+    else:
+        thousands, remainder = divide_with_remainder(number, 1000)
+        if remainder ==0:
+            return f"{int_under_1000_to_str(thousands)} thousand"
+        else:
+            return f"{int_under_1000_to_str(thousands)} thousand, {int_under_1000_to_str(remainder)}"
         
 def int_under_1000_to_str(number):
-    return "umm..."
+    if number < 100:
+        return int_under_100_to_str(number)
+    else:
+        hundreds, remainder = divide_with_remainder(number, 100)
+        if remainder == 0:
+            return f"{int_under_10_to_str(hundreds)} hundred"
+        else:
+            return f"{int_under_10_to_str(hundreds)} hundred and {int_under_100_to_str(remainder)}"
 
 def int_under_100_to_str(number):
-    return "umm..."
+    if number < 10:
+        return int_under_10_to_str(number)
+    elif number < 20:
+        return int_under_20_to_str(number)
+    else:
+        tens, ones = divide_with_remainder(number, 10)
+        if ones == 0:
+            return TENS_NAMES[tens]
+        else:
+            return f"{TENS_NAMES[tens]}-{int_under_10_to_str(ones)}"
 
 def int_under_20_to_str(number):
-    return "umm..."
+    if number < 10:
+        return int_under_10_to_str(number)
+    else:
+        return TWEEN_AND_TEEN_NAMES[number - 10]
+
 
 def int_under_10_to_str(number):
-    return "umm..."
+    return DIGIT_NAMES[number]
 
 def divide_with_remainder(dividend, divisor):
     """Divides one number by another, using whole-number division.