diff --git a/DSA/__init__.py b/DSA/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/DSA/number_theory/__init__.py b/DSA/number_theory/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/DSA/number_theory/prime_number.py b/DSA/number_theory/prime_number.py
new file mode 100644
index 0000000..e2ad249
--- /dev/null
+++ b/DSA/number_theory/prime_number.py
@@ -0,0 +1,29 @@
+# prime number is only divisible by 1 and that number itself
+# prime number is greater then 1
+
+import math
+
+
+def is_prime(number: int):
+    """Brute force"""
+    # if number is 1 or less then 1 then its not a prime number
+    if number <= 1:
+        return False
+
+    # iter every item which starts from 2 and ends before number:
+    limit = int(math.sqrt(number + 1))
+    for value in range(2, limit):
+        # if number is divisible by value: which is number less then the number
+        # then its not prime number as prime number can't be divided by any other number itself
+        print("dude!")
+        if number % value == 0:
+            return False
+
+    if limit <= 2 and number % limit == 0:
+        return False
+
+    return True
+
+
+number = 3
+print(f"Number {number} is prime: {is_prime(number)}")
diff --git a/HackerRank/linked_list_insert_position.py b/HackerRank/linked_list_insert_position.py
index 68004ea..c2fc8c7 100644
--- a/HackerRank/linked_list_insert_position.py
+++ b/HackerRank/linked_list_insert_position.py
@@ -77,3 +77,141 @@ def print_nodes(self):
             result.append(current_head.data)
             current_head = current_head.next
         return result
+
+
+def push_at(self, newElement, position):
+
+    # 1. allocate node to new element
+    newNode = Node(newElement)
+
+    # 2. check if the position is > 0
+    if position < 1:
+        print("\nposition should be >= 1.")
+    elif position == 1:
+
+        # 3. if the position is 1, make next of the
+        #   new node as head and new node as head
+        newNode.next = self.head
+        self.head = newNode
+    else:
+
+        # 4. Else, make a temp node and traverse to the
+        #   node previous to the position
+        temp = self.head
+        for i in range(1, position - 1):
+            if temp != None:
+                temp = temp.next
+
+        # 5. If the previous node is not null, make
+        #   newNode next as temp next and temp next
+        #   as newNode.
+        if temp != None:
+            newNode.next = temp.next
+            temp.next = newNode
+        else:
+
+            # 6. When the previous node is null
+            print("\nThe previous node is null.")
+
+
+# Python3 program for insertion in a single linked
+# list at a specified position
+
+
+# A linked list Node
+class Node:
+    def __init__(self, data):
+        self.data = data
+        self.nextNode = None
+
+
+# function to create and return a Node
+def getNode(data):
+
+    # allocating space
+    newNode = Node(data)
+    return newNode
+
+
+# function to insert a Node at required position
+def insertPos(headNode, position, data):
+    head = headNode
+
+    # This condition to check whether the
+    # position given is valid or not.
+    if position < 1:
+        print("Invalid position!")
+
+    if position == 1:
+        newNode = Node(data)
+        newNode.nextNode = headNode
+        head = newNode
+
+    else:
+
+        # Keep looping until the position is zero
+        while position != 0:
+            position -= 1
+
+            if position == 1:
+
+                # adding Node at required position
+                newNode = getNode(data)
+
+                # Making the new Node to point to
+                # the old Node at the same position
+                newNode.nextNode = headNode.nextNode
+
+                # Replacing headNode with new Node
+                # to the old Node to point to the new Node
+                headNode.nextNode = newNode
+                break
+
+            headNode = headNode.nextNode
+            if headNode == None:
+                break
+        if position != 1:
+            print("position out of range")
+    return head
+
+
+# This function prints contents
+# of the linked list
+def printList(head):
+    while head != None:
+        print(" " + str(head.data), end="")
+        head = head.nextNode
+    print()
+
+
+# Driver Code
+if __name__ == "__main__":
+
+    # Creating the list 3.5.8.10
+    head = getNode(3)
+    head.nextNode = getNode(5)
+    head.nextNode.nextNode = getNode(8)
+    head.nextNode.nextNode.nextNode = getNode(10)
+    print("Linked list before insertion: ", end="")
+    printList(head)
+    data = 12
+    position = 3
+    head = insertPos(head, position, data)
+    print("Linked list after insertion of 12 at position 3: ", end="")
+    printList(head)
+
+    # front of the linked list
+    data = 1
+    position = 1
+    head = insertPos(head, position, data)
+    print("Linked list after insertion of 1 at position 1: ", end="")
+    printList(head)
+
+    # insertion at end of the linked list
+    data = 15
+    position = 7
+    head = insertPos(head, position, data)
+    print("Linked list after insertion of 15 at position 7: ", end="")
+    printList(head)
+
+# This code iscontributed by rutvik_56
diff --git a/__init__.py b/__init__.py
index e2abbd3..6a0e991 100644
--- a/__init__.py
+++ b/__init__.py
@@ -3,3 +3,4 @@
 
 path = os.getcwd()
 sys.path.append(path)
+
diff --git a/tests/test_number_theory.py b/tests/test_number_theory.py
new file mode 100644
index 0000000..0be9094
--- /dev/null
+++ b/tests/test_number_theory.py
@@ -0,0 +1,4 @@
+def test_is_prime():
+    from DSA.number_theory.prime_number import is_prime
+    
+    
\ No newline at end of file