diff --git a/.idea/.idea.Leetcode/.idea/workspace.xml b/.idea/.idea.Leetcode/.idea/workspace.xml
index 34f7850..b94eece 100644
--- a/.idea/.idea.Leetcode/.idea/workspace.xml
+++ b/.idea/.idea.Leetcode/.idea/workspace.xml
@@ -88,9 +88,9 @@
   </component>
   <component name="ChangeListManager">
     <list default="true" id="11f2de1c-1ee5-4aa4-91e6-11975ebd421f" name="Changes" comment="">
-      <change afterPath="$PROJECT_DIR$/150. Evaluate Reverse Polish Notation/150. Evaluate Reverse Polish Notation.csproj" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/150. Evaluate Reverse Polish Notation/Program.cs" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/150. Evaluate Reverse Polish Notation/Solution.cs" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/9. Palindrome Number/9. Palindrome Number.csproj" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/9. Palindrome Number/Program.cs" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/9. Palindrome Number/Solution.cs" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/.idea/.idea.Leetcode/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/.idea.Leetcode/.idea/workspace.xml" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/Leetcode.sln" beforeDir="false" afterPath="$PROJECT_DIR$/Leetcode.sln" afterDir="false" />
     </list>
@@ -128,6 +128,7 @@
   "keyToString": {
     ".NET Project.14. Longest Common Prefix.executor": "Run",
     ".NET Project.150. Evaluate Reverse Polish Notation.executor": "Run",
+    ".NET Project.9. Palindrome Number.executor": "Run",
     "ASKED_ADD_EXTERNAL_FILES": "true",
     "RunOnceActivity.OpenProjectViewOnStart": "true",
     "RunOnceActivity.ShowReadmeOnStart": "true",
@@ -150,7 +151,7 @@
     ]
   }
 }]]></component>
-  <component name="RunManager" selected=".NET Project.150. Evaluate Reverse Polish Notation">
+  <component name="RunManager" selected=".NET Project.9. Palindrome Number">
     <configuration name="101. Symmetric Tree" type="DotNetProject" factoryName=".NET Project">
       <option name="EXE_PATH" value="" />
       <option name="PROGRAM_PARAMETERS" value="" />
@@ -1645,8 +1646,27 @@
         <option name="Build" />
       </method>
     </configuration>
+    <configuration name="9. Palindrome Number" type="DotNetProject" factoryName=".NET Project" temporary="true">
+      <option name="EXE_PATH" value="$PROJECT_DIR$/9. Palindrome Number/bin/Debug/net8.0/9. Palindrome Number" />
+      <option name="PROGRAM_PARAMETERS" value="" />
+      <option name="WORKING_DIRECTORY" value="$PROJECT_DIR$/9. Palindrome Number/bin/Debug/net8.0" />
+      <option name="PASS_PARENT_ENVS" value="1" />
+      <option name="USE_EXTERNAL_CONSOLE" value="0" />
+      <option name="USE_MONO" value="0" />
+      <option name="RUNTIME_ARGUMENTS" value="" />
+      <option name="PROJECT_PATH" value="$PROJECT_DIR$/9. Palindrome Number/9. Palindrome Number.csproj" />
+      <option name="PROJECT_EXE_PATH_TRACKING" value="1" />
+      <option name="PROJECT_ARGUMENTS_TRACKING" value="1" />
+      <option name="PROJECT_WORKING_DIRECTORY_TRACKING" value="1" />
+      <option name="PROJECT_KIND" value="DotNetCore" />
+      <option name="PROJECT_TFM" value="net8.0" />
+      <method v="2">
+        <option name="Build" />
+      </method>
+    </configuration>
     <recent_temporary>
       <list>
+        <item itemvalue=".NET Project.9. Palindrome Number" />
         <item itemvalue=".NET Project.150. Evaluate Reverse Polish Notation" />
         <item itemvalue=".NET Project.14. Longest Common Prefix" />
       </list>
@@ -1662,7 +1682,7 @@
       <updated>1678030074860</updated>
       <workItem from="1678030078340" duration="114000" />
       <workItem from="1680804946367" duration="3697000" />
-      <workItem from="1706644472303" duration="6672000" />
+      <workItem from="1706644472303" duration="7691000" />
     </task>
     <servers />
   </component>
diff --git a/9. Palindrome Number/9. Palindrome Number.csproj b/9. Palindrome Number/9. Palindrome Number.csproj
new file mode 100644
index 0000000..67b341f
--- /dev/null
+++ b/9. Palindrome Number/9. Palindrome Number.csproj	
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net8.0</TargetFramework>
+        <RootNamespace>_9._Palindrome_Number</RootNamespace>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+</Project>
diff --git a/9. Palindrome Number/Program.cs b/9. Palindrome Number/Program.cs
new file mode 100644
index 0000000..ee812bf
--- /dev/null
+++ b/9. Palindrome Number/Program.cs	
@@ -0,0 +1,6 @@
+// See https://aka.ms/new-console-template for more information
+
+using _9._Palindrome_Number;
+
+var sol = new Solution();
+Console.WriteLine(sol.IsPalindrome(0));
\ No newline at end of file
diff --git a/9. Palindrome Number/Solution.cs b/9. Palindrome Number/Solution.cs
new file mode 100644
index 0000000..80222dd
--- /dev/null
+++ b/9. Palindrome Number/Solution.cs	
@@ -0,0 +1,25 @@
+namespace _9._Palindrome_Number;
+
+public class Solution
+{
+    public bool IsPalindrome(int x)
+    {
+        if (x < 0)
+            return false;
+        if (x < 10)
+            return true;
+        List<byte> digits = new List<byte>(32);
+        while (x != 0)
+        {
+            digits.Add((byte)(x%10));
+            x /= 10;
+        }
+
+        int half = digits.Count / 2;
+        for (int i = 0; i < half; i++)
+            if (digits[i] != digits[digits.Count - 1 - i])
+                return false;
+
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/Leetcode.sln b/Leetcode.sln
index 06bdebe..ee121b5 100644
--- a/Leetcode.sln
+++ b/Leetcode.sln
@@ -169,6 +169,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "14. Longest Common Prefix",
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "150. Evaluate Reverse Polish Notation", "150. Evaluate Reverse Polish Notation\150. Evaluate Reverse Polish Notation.csproj", "{10A95EED-FD1D-40E7-B9E0-2DD48BE05AB9}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "9. Palindrome Number", "9. Palindrome Number\9. Palindrome Number.csproj", "{1397373A-47E9-4E22-8FE5-82376C7FACA1}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -507,6 +509,10 @@ Global
 		{10A95EED-FD1D-40E7-B9E0-2DD48BE05AB9}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{10A95EED-FD1D-40E7-B9E0-2DD48BE05AB9}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{10A95EED-FD1D-40E7-B9E0-2DD48BE05AB9}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1397373A-47E9-4E22-8FE5-82376C7FACA1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1397373A-47E9-4E22-8FE5-82376C7FACA1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1397373A-47E9-4E22-8FE5-82376C7FACA1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1397373A-47E9-4E22-8FE5-82376C7FACA1}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE