I have solve the answer for Exercise-3.

divide_reverse_count/divide_reverse_count.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.28010.2036
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "divide_reverse_count", "divide_reverse_count\divide_reverse_count.csproj", "{EAF6365A-AE6C-47DC-B642-B010FD28054D}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{EAF6365A-AE6C-47DC-B642-B010FD28054D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{EAF6365A-AE6C-47DC-B642-B010FD28054D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{EAF6365A-AE6C-47DC-B642-B010FD28054D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{EAF6365A-AE6C-47DC-B642-B010FD28054D}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {8D3D0E0D-AAC3-4E9B-863A-9B3235DADCBB}
+	EndGlobalSection
+EndGlobal

divide_reverse_count/divide_reverse_count/App.config

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+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+    <startup> 
+        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
+    </startup>
+</configuration>

divide_reverse_count/divide_reverse_count/Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace divide_reverse_count
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            // Console.WriteLine(Reverse(1234));
+            //Console.WriteLine(divide(36));
+            //Console.WriteLine(count(12345));
+            //Console.WriteLine(countreverse(123456));
+            //Console.WriteLine(evencount(123));
+            //Console.WriteLine(amstrong(153));
+            //Console.WriteLine(firstdigit(123456));
+            // Console.WriteLine(lastdigit(123456));
+            //Console.WriteLine(firstlast(12351));
+            //Console.WriteLine(palindrome(6226));
+            //if (IsPrime(6)==true)
+            //{
+            //    Console.WriteLine("is prime");
+            //}
+            //else
+            //{
+            //    Console.WriteLine("not prime");
+            //}
+            // Console.WriteLine(SumOFPrimeNumberless(20));
+
+            Console.WriteLine(SumOFPerfectSquare(30));
+        }
+        public static int Reverse(int n)
+        {
+            int rev = 0;
+            while (n > 0)
+            {
+                int temp = n % 10;
+                rev = rev * 10 + temp;
+                n = n / 10;
+            }
+            return rev;
+        }
+        public static bool divide(int n)
+        {
+            int temp = n % 10;
+            if (n % temp == 0)
+            {
+                return true;
+            }
+            return false;
+        }
+        public static int count(int n)
+        {
+            int count = 0;
+
+            while (n > 0)
+            {
+                n = n / 10;
+                count++;
+            }
+
+            return count;
+
+        }
+        public static int countreverse(int n)
+        {
+            int count = 0;
+            int rev = 0;
+            while (n > 0)
+            {
+                int temp = n % 10;
+                rev = rev * 10 + temp;
+                n = n / 10;
+                count++;
+            }
+
+            return count;
+        }
+        public static int evencount(int n)
+        {
+
+            int count = 0;
+            int evencount = 0;
+            int oddcount = 0;
+            // int rev = 0;
+            while (n > 0)
+            {
+                int temp = n % 10;
+                // rev = rev * 10 + temp;
+                n = n / 10;
+                if (temp % 2 == 0)
+                {
+                    evencount++;
+                    Console.WriteLine("even:" + evencount);
+                }
+                //return evencount;
+                else if (temp % 2 != 0)
+                {
+                    oddcount++;
+                    Console.WriteLine("odd:" + oddcount);
+                }
+
+            }
+            return count;
+        }
+        public static bool amstrong(int n)
+        {
+            bool Flag = true;
+            int count;
+            count = (int)(Math.Log10(n) + 1);
+            double sum = 0;
+            int rem;
+            int temp = n;
+            while (n != 0)
+            {
+                rem = n % 10; ;
+                sum = sum + (Math.Pow(rem, count));
+                n = n / 10;
+            }
+            if (sum == temp)
+            {
+                return Flag;
+            }
+            else
+            {
+                return false;
+            }
+        }
+        public static int firstdigit(int n)
+        {
+            while (n > 10)
+            {
+                n = n / 10;
+            }
+            return n;
+        }
+        public static int lastdigit(int n)
+        {
+            n = n % 10;
+            return n;
+        }
+        public static bool firstlast(int n)
+        {
+            bool flag = true;
+
+            if (firstdigit(n) == lastdigit(n))
+            {
+                return flag;
+            }
+            return false;
+
+        }
+        public static bool palindrome(int n)
+        {
+            bool flag = true;
+            int reverse = 0;
+            int rem;
+            int temp = n;
+            while (n > 0)
+            {
+
+                rem = n % 10;
+                reverse = reverse * 10 + rem;
+                n = n / 10;
+            }
+            if (temp == reverse)
+            {
+                return flag;
+            }
+            else
+            {
+                return false;
+            }
+        }
+        public static bool IsPrime(int n)
+        {
+
+            bool flag = true;
+            if (n <= 1)
+            {
+                return false;
+            }
+            if (n == 2)
+            {
+                return flag;
+            }
+            // for (int i = 2; i < Math.Sqrt(n) + 1; i++)
+            int i = 2;
+            while (i < Math.Sqrt(n) + 1)
+            {
+                if (n % i == 0)
+                {
+                    flag = false;
+                }
+                i++;
+            }
+            return flag;
+        }
+        public static int SumOFPrimeNumberless(int n)
+        {
+
+            // bool flag = true;
+            int sum = 0;
+            for (int i = 2; i <= n; i++)
+            {
+                if (IsPrime(i))
+                {
+                    // Console.WriteLine(i);
+                    sum += i;
+                }
+            }
+            return sum;
+        }
+        public static bool IsPerfectSquare(int n)
+        {
+            bool flag = true;
+            double x = Math.Sqrt(n);
+            double y = Math.Round(x);
+            if (x - y == 0)
+            {
+                return flag;
+            }
+            else
+            {
+
+                return false;
+            }
+        }
+        public static int SumOFPerfectSquare(int n)
+        {
+            int sum = 0;
+            for (int i = 1; i <= n; i++)
+            {
+                if (IsPerfectSquare(i))
+                {
+                    sum = sum + i;
+                }
+            }
+            return sum; ;
+        }
+    }
+}

divide_reverse_count/divide_reverse_count/Properties/AssemblyInfo.cs

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+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// General Information about an assembly is controlled through the following
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyTitle("divide_reverse_count")]
+[assembly: AssemblyDescription("")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("")]
+[assembly: AssemblyProduct("divide_reverse_count")]
+[assembly: AssemblyCopyright("Copyright ©  2019")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible
+// to COM components.  If you need to access a type in this assembly from
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// The following GUID is for the ID of the typelib if this project is exposed to COM
+[assembly: Guid("eaf6365a-ae6c-47dc-b642-b010fd28054d")]
+
+// Version information for an assembly consists of the following four values:
+//
+//      Major Version
+//      Minor Version
+//      Build Number
+//      Revision
+//
+// You can specify all the values or you can default the Build and Revision Numbers
+// by using the '*' as shown below:
+// [assembly: AssemblyVersion("1.0.*")]
+[assembly: AssemblyVersion("1.0.0.0")]
+[assembly: AssemblyFileVersion("1.0.0.0")]

divide_reverse_count/divide_reverse_count/divide_reverse_count.csproj

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+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{EAF6365A-AE6C-47DC-B642-B010FD28054D}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <RootNamespace>divide_reverse_count</RootNamespace>
+    <AssemblyName>divide_reverse_count</AssemblyName>
+    <TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+    <Deterministic>true</Deterministic>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Core" />
+    <Reference Include="System.Xml.Linq" />
+    <Reference Include="System.Data.DataSetExtensions" />
+    <Reference Include="Microsoft.CSharp" />
+    <Reference Include="System.Data" />
+    <Reference Include="System.Net.Http" />
+    <Reference Include="System.Xml" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="Program.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="App.config" />
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>

divide_reverse_count/divide_reverse_count/obj/Debug/divide_reverse_count.csproj.CoreCompileInputs.cache

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+e94166f8473d37a7088a8641e0119a67f8219728