diff --git a/conversions/roman_numerals.py b/conversions/roman_numerals.py
index 75af2ac72882..2e1d5f7026a5 100644
--- a/conversions/roman_numerals.py
+++ b/conversions/roman_numerals.py
@@ -1,4 +1,16 @@
 ROMAN = [
+    (1000000, "M_"),
+    (900000, "C_M_"),
+    (500000, "D_"),
+    (400000, "C_D_"),
+    (100000, "C_"),
+    (90000, "X_C_"),
+    (50000, "L_"),
+    (40000, "X_L_"),
+    (10000, "X_"),
+    (9000, "I_X_"),
+    (5000, "V_"),
+    (4000, "I_V_"),
     (1000, "M"),
     (900, "CM"),
     (500, "D"),
@@ -15,40 +27,26 @@
 ]
 
 
-def roman_to_int(roman: str) -> int:
-    """
-    LeetCode No. 13 Roman to Integer
-    Given a roman numeral, convert it to an integer.
-    Input is guaranteed to be within the range from 1 to 3999.
-    https://en.wikipedia.org/wiki/Roman_numerals
-    >>> tests = {"III": 3, "CLIV": 154, "MIX": 1009, "MMD": 2500, "MMMCMXCIX": 3999}
-    >>> all(roman_to_int(key) == value for key, value in tests.items())
-    True
-    """
-    vals = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}
-    total = 0
-    place = 0
-    while place < len(roman):
-        if (place + 1 < len(roman)) and (vals[roman[place]] < vals[roman[place + 1]]):
-            total += vals[roman[place + 1]] - vals[roman[place]]
-            place += 2
+def roman_to_int(roman):
+    vals = {roman: arabic for arabic, roman in ROMAN}
+    i, total = 0, 0
+    while i < len(roman):
+        if i + 1 < len(roman) and roman[i + 1] == "_":
+            total += vals[roman[i] + "_"]
+            i += 2
         else:
-            total += vals[roman[place]]
-            place += 1
+            total += vals[roman[i]]
+            i += 1
     return total
 
 
-def int_to_roman(number: int) -> str:
-    """
-    Given a integer, convert it to an roman numeral.
-    https://en.wikipedia.org/wiki/Roman_numerals
-    >>> tests = {"III": 3, "CLIV": 154, "MIX": 1009, "MMD": 2500, "MMMCMXCIX": 3999}
-    >>> all(int_to_roman(value) == key for key, value in tests.items())
-    True
-    """
+def int_to_roman(number):
+    if not isinstance(number, int) or number <= 0:
+        raise ValueError("Input must be a positive integer greater than 0")
+
     result = []
     for arabic, roman in ROMAN:
-        (factor, number) = divmod(number, arabic)
+        factor, number = divmod(number, arabic)
         result.append(roman * factor)
         if number == 0:
             break