diff --git a/Numbers/NumberFactory/AbstractNumbers.cs b/Numbers/NumberFactory/AbstractNumbers.cs
index 0c5a724..aa4e84e 100644
--- a/Numbers/NumberFactory/AbstractNumbers.cs
+++ b/Numbers/NumberFactory/AbstractNumbers.cs
@@ -8,8 +8,7 @@ namespace Numbers.NumberFactory;
 /// <inheritdoc cref="INumbers" />
 public abstract class AbstractNumbers : INumbers
 {
-    // TODO
-    // private readonly List<long> _list;
+    private readonly List<long> _list;
 
     /// <summary>
     ///     Creates a new instance of <see cref="AbstractNumbers" /> with the given bounds.
@@ -19,15 +18,22 @@ public abstract class AbstractNumbers : INumbers
     /// <param name="upperBound">Upper bound of the number range</param>
     protected AbstractNumbers(long lowerBound, long upperBound)
     {
-        // TODO
+        LowerBound = lowerBound;
+        UpperBound = upperBound;
+        _list = [];
+        GenerateNumbers();
     }
 
     public long this[int index]
     {
         get
         {
-            // TODO
-            return -1L;
+            if (index < 0 || index >= _list.Count)
+            {
+                return -1;
+            }
+            
+            return _list[index];
         }
     }
 
@@ -35,15 +41,20 @@ public abstract class AbstractNumbers : INumbers
 
     public long UpperBound { get; }
 
-    public int Length => -1; // TODO
+    public int Length => _list.Count;
+    public IEnumerator<long> GetEnumerator() => new NumbersEnumerator(_list);
 
-    public IEnumerator<long> GetEnumerator() => null!; // TODO
-
-    IEnumerator IEnumerable.GetEnumerator() => null!; // TODO
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
 
     private void GenerateNumbers()
     {
-        // TODO
+        for (var i = LowerBound; i <= UpperBound; i++)
+        {
+            if (PickNumber(i))
+            {
+                _list.Add(i);
+            }
+        }
     }
 
     /// <summary>
diff --git a/Numbers/NumberFactory/Factory.cs b/Numbers/NumberFactory/Factory.cs
index 8cd0757..643fc67 100644
--- a/Numbers/NumberFactory/Factory.cs
+++ b/Numbers/NumberFactory/Factory.cs
@@ -16,8 +16,19 @@ public static class Factory
     /// <returns>Appropriate instance or null if requested type is unknown</returns>
     public static INumbers Create(NumberType type, long lowerBound, long upperBound)
     {
-        // TODO
-        return null!;
+        switch (type)
+        {
+            case NumberType.Even:
+                return new EvenNumbers(lowerBound, upperBound);
+            case NumberType.Odd:
+                return new OddNumbers(lowerBound, upperBound);
+            case NumberType.Prime:
+                return new PrimeNumbers(lowerBound, upperBound);
+            case NumberType.Square:
+                return new SquareNumbers(lowerBound, upperBound);
+            default:
+                return null!;
+        }
     }
 }
 
diff --git a/Numbers/NumberFactory/NumberImpls/EvenNumbers.cs b/Numbers/NumberFactory/NumberImpls/EvenNumbers.cs
index c53359a..58bfe90 100644
--- a/Numbers/NumberFactory/NumberImpls/EvenNumbers.cs
+++ b/Numbers/NumberFactory/NumberImpls/EvenNumbers.cs
@@ -6,5 +6,5 @@ namespace Numbers.NumberFactory.NumberImpls;
 /// <inheritdoc cref="AbstractNumbers" />
 public sealed class EvenNumbers(long lowerBound, long upperBound) : AbstractNumbers(lowerBound, upperBound)
 {
-    protected override bool PickNumber(long number) => false; // TODO
+    protected override bool PickNumber(long number) => number % 2 == 0;
 }
diff --git a/Numbers/NumberFactory/NumberImpls/OddNumbers.cs b/Numbers/NumberFactory/NumberImpls/OddNumbers.cs
index 6378f98..59eb2cf 100644
--- a/Numbers/NumberFactory/NumberImpls/OddNumbers.cs
+++ b/Numbers/NumberFactory/NumberImpls/OddNumbers.cs
@@ -6,5 +6,5 @@ namespace Numbers.NumberFactory.NumberImpls;
 /// <inheritdoc cref="AbstractNumbers" />
 public sealed class OddNumbers(long lowerBound, long upperBound) : AbstractNumbers(lowerBound, upperBound)
 {
-    protected override bool PickNumber(long number) => false; // TODO
+    protected override bool PickNumber(long number) => number % 2 != 0;
 }
diff --git a/Numbers/NumberFactory/NumberImpls/PrimeNumbers.cs b/Numbers/NumberFactory/NumberImpls/PrimeNumbers.cs
index 02fc1d3..4d936d8 100644
--- a/Numbers/NumberFactory/NumberImpls/PrimeNumbers.cs
+++ b/Numbers/NumberFactory/NumberImpls/PrimeNumbers.cs
@@ -6,5 +6,30 @@ namespace Numbers.NumberFactory.NumberImpls;
 /// <inheritdoc cref="AbstractNumbers" />
 public sealed class PrimeNumbers(long lowerBound, long upperBound) : AbstractNumbers(lowerBound, upperBound)
 {
-    protected override bool PickNumber(long number) => false; // TODO
+    protected override bool PickNumber(long number)
+    {
+        if (number < 2)
+        {
+            return false;
+        }
+        if (number == 2)
+        {
+            return true;
+        }
+        if (number % 2 == 0)
+        {
+            return false;
+        }
+        
+        long sqrtNum = (long)Math.Sqrt(number);
+        for (int i = 3; i <= sqrtNum; i += 2)
+        {
+            if (number % i == 0)
+            {
+                return false;
+            }
+        }
+        
+        return true;
+    }
 }
diff --git a/Numbers/NumberFactory/NumberImpls/SquareNumbers.cs b/Numbers/NumberFactory/NumberImpls/SquareNumbers.cs
index f023fa9..f316073 100644
--- a/Numbers/NumberFactory/NumberImpls/SquareNumbers.cs
+++ b/Numbers/NumberFactory/NumberImpls/SquareNumbers.cs
@@ -6,5 +6,5 @@ namespace Numbers.NumberFactory.NumberImpls;
 /// <inheritdoc cref="AbstractNumbers" />
 public sealed class SquareNumbers(long lowerBound, long upperBound) : AbstractNumbers(lowerBound, upperBound)
 {
-    protected override bool PickNumber(long number) => false; // TODO
+    protected override bool PickNumber(long number) => Math.Sqrt(number) % 1 == 0;
 }
diff --git a/Numbers/NumberFactory/NumbersEnumerator.cs b/Numbers/NumberFactory/NumbersEnumerator.cs
index 7f0f4df..6d0b3bc 100644
--- a/Numbers/NumberFactory/NumbersEnumerator.cs
+++ b/Numbers/NumberFactory/NumbersEnumerator.cs
@@ -14,26 +14,44 @@ public sealed class NumbersEnumerator : IEnumerator<long>
     /// <param name="list">List to iterate over</param>
     public NumbersEnumerator(List<long> list)
     {
-        // TODO
-        List = null!;
+        List = list;
+        Index = -1;
     }
 
     private int Index { get; set; }
     private List<long> List { get; }
 
-    public long Current => -1L; // TODO
-
-    public void Dispose() 
+    public long Current
     {
-        // TODO?
+        get
+        {
+            if (Index < 0 || Index >= List.Count)
+            {
+                return -1;
+            }
+            
+            return List[Index];
+        }
     }
 
-    object IEnumerator.Current => null!; // TODO
+    public void Dispose() { }
 
-    public bool MoveNext() => false; // TODO
+    object IEnumerator.Current => Current;
+
+    public bool MoveNext()
+    {
+        if (Index >= List.Count - 1)
+        {
+            return false;
+        }
+
+        Index++;
+        return true;
+
+    }
 
     public void Reset()
     {
-        // TODO
+        Index = -1;
     }
 }
diff --git a/Numbers/NumberString/DigitEnumerator.cs b/Numbers/NumberString/DigitEnumerator.cs
index d08bc0f..fda90e3 100644
--- a/Numbers/NumberString/DigitEnumerator.cs
+++ b/Numbers/NumberString/DigitEnumerator.cs
@@ -8,9 +8,8 @@ namespace Numbers.NumberString;
 /// <inheritdoc cref="IEnumerator{T}"/>
 public sealed class DigitEnumerator : IEnumerator<int>
 {
-    // TODO
-    // private readonly string _text;
-    // private int _index;
+    private readonly string _text;
+    private int _index;
 
     /// <summary>
     ///     Creates a new instance of <see cref="DigitEnumerator"/> based on the given text.
@@ -19,35 +18,42 @@ public sealed class DigitEnumerator : IEnumerator<int>
     /// <param name="text">The text to iterate over (containing both letters and digits)</param>
     public DigitEnumerator(string text)
     {
-        // TODO
+        _text = text;
+        _index = -1;
     }
 
     public bool MoveNext()
     {
-        // TODO
+        while (++_index < _text.Length)
+        {
+            if (char.IsDigit(_text[_index]))
+            {
+                return true;
+            }
+        }
         return false;
     }
 
     public void Reset()
     {
-        // TODO
+        _index = -1;
     }
 
     public int Current
     {
         get
         {
-            // TODO
-            return -1;
-
-            //static int GetDigit(char c) => c - '0';
+            if (_index < 0 || _index >= _text.Length || !char.IsDigit(_text[_index]))
+            {
+                return -1;
+            }
+            
+            return GetDigit(_text[_index]);
+            static int GetDigit(char c) => c - '0';
         }
     }
 
-    object IEnumerator.Current => null!; // TODO
+    object IEnumerator.Current => Current;
 
-    public void Dispose()
-    {
-        // TODO?
-    }
+    public void Dispose() { }
 }
diff --git a/Numbers/NumberString/NumberString.cs b/Numbers/NumberString/NumberString.cs
index 6377f73..ddbc8e7 100644
--- a/Numbers/NumberString/NumberString.cs
+++ b/Numbers/NumberString/NumberString.cs
@@ -9,9 +9,8 @@ namespace Numbers.NumberString;
 /// <inheritdoc cref="IComparable{T}" />
 public sealed class NumberString : IEnumerable<int>, IComparable<NumberString>
 {
-    // TODO
-    // private readonly string _text;
-    // private int? _numericValue;
+    private readonly string _text;
+    private int? _numericValue;
 
     /// <summary>
     ///     Creates a new instance of <see cref="NumberString" /> based on the given text.
@@ -20,13 +19,15 @@ public sealed class NumberString : IEnumerable<int>, IComparable<NumberString>
     /// <param name="text">A string containing digits and letters</param>
     public NumberString(string text)
     {
-        // TODO
+        _text = text;
+        string digitsOnly = new string(text.Where(char.IsDigit).ToArray());
+        _numericValue = digitsOnly.Length > 0 ? int.Parse(digitsOnly) : 0;
     }
 
     /// <summary>
     ///     Gets the numeric value contained in the number string
     /// </summary>
-    public int NumericValue => -1; // TODO
+    public int NumericValue => _numericValue ?? 0;
 
     /// <summary>
     ///     Gets the digit at the given index.
@@ -37,30 +38,47 @@ public sealed class NumberString : IEnumerable<int>, IComparable<NumberString>
     {
         get
         {
-            // TODO
-            return -1;
+            string numberString = _numericValue.HasValue ? _numericValue.Value.ToString() : string.Empty;
+            if (index < 0 || index >= numberString.Length || numberString == string.Empty)
+            {
+                return -1;
+            }
+            return GetDigit(numberString[index]);
+            static int GetDigit(char c) => c - '0';
         }
     }
 
-    public int CompareTo(NumberString? other) => -1; // TODO
+    public int CompareTo(NumberString? other)
+    {
+        if (ReferenceEquals(this, other))
+        {
+            return 1;
+        }
+        
+        return NumericValue.CompareTo(other?.NumericValue);
+    }
 
-    public IEnumerator<int> GetEnumerator() => null!; // TODO
+    public IEnumerator<int> GetEnumerator() => new DigitEnumerator(_text);
 
-    IEnumerator IEnumerable.GetEnumerator() => null!; // TODO
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
 
     public override bool Equals(object? obj)
     {
-        // TODO
-        return false;
+        if (obj is not NumberString numberString)
+        {
+            return false;
+        }
+
+        return numberString._numericValue == _numericValue;
     }
 
-    public override int GetHashCode() => -1; // TODO
+    public override int GetHashCode() => _numericValue?.GetHashCode() ?? 0;
 
-    public static bool operator >(NumberString a, NumberString b) => false; // TODO
+    public static bool operator >(NumberString a, NumberString b) => a.CompareTo(b) > 0;
 
-    public static bool operator <(NumberString a, NumberString b) => false; // TODO
+    public static bool operator <(NumberString a, NumberString b) => a.CompareTo(b) < 0;
 
-    public static bool operator ==(NumberString a, NumberString b) => false; // TODO
+    public static bool operator ==(NumberString a, NumberString b) => a?.Equals(b) ?? ReferenceEquals(b, null);
 
-    public static bool operator !=(NumberString a, NumberString b) => false; // TODO
+    public static bool operator !=(NumberString a, NumberString b) => !(a == b);
 }