Perfect Numbers

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Created by: Team Maths -, Last Updated: June 24, 2024

Perfect Numbers

Perfect numbers are a fascinating mathematical phenomenon that has captivated scholars for centuries. This guide aims to demystify the concept of perfect numbers through clear definitions, engaging examples, and practical applications. By exploring the unique properties and patterns of perfect numbers, we hope to inspire a deeper appreciation for the elegance and complexity of mathematics, making it accessible and enjoyable for learners of all levels.

What are Perfect Numbers?

Perfect numbers are a unique class of positive integers that are equal to the sum of their proper divisors, excluding themselves. This distinctive property makes them a topic of great interest in number theory. Perfect numbers are rare and exhibit a harmonious balance that has fascinated mathematicians since ancient times. Understanding what constitutes a perfect number helps illuminate the rich interconnections within mathematics, providing insight into the symmetry and order that underpin the number system.

What is the Best Example of a Perfect Number?

The best example of a perfect number is 6. It is the smallest perfect number and illustrates the defining characteristic perfectly: the sum of its proper divisors (1, 2, and 3) equals 6 itself (1 + 2 + 3 = 6). This example not only demonstrates the concept of perfect numbers clearly but also serves as a gateway to exploring more complex perfect numbers and their properties. By studying 6, students can grasp the foundational principles of perfect numbers, setting the stage for deeper mathematical exploration and discovery.

History of Perfect Numbers

Perfect numbers have intrigued mathematicians since ancient times, with their origins tracing back to the work of Euclid around 300 BC. Euclid first defined perfect numbers in his “Elements,” demonstrating that numbers of the form are perfect when 2p-1 is prime, a condition now known as a Mersenne prime. The earliest example, 6, was considered a symbol of perfection in Greek mathematics. Throughout history, perfect numbers have held mystical and mathematical significance, captivating scholars like Pythagoras and later, medieval mathematicians who linked them to celestial harmony and religious symbolism.

Best Example: The number 6, the sum of its divisors (1, 2, and 3), is the smallest and most anciently recognized perfect number, illustrating the concept’s historical roots.

How to Find a Perfect Number?

n 2n-1 2n-1(Evaluation) 2n-1×2n-1
1 1 1
2 2 3 (prime number) 6 (perfect number)
3 4 7 (prime number) 28 (perfect number)
4 8 15
5 16 31 (prime number) 496 (perfect number)
6 32 63
7 64 127 (prime number) 8128 (perfect number)
8 128 255
9 256 511
10 512 1023

Finding a perfect number involves a few systematic steps, based on the properties that define these numbers. Here’s how you can find a perfect number:

Step 1: Understand the Definition

  • Recognize that a perfect number is a positive integer that is equal to the sum of its proper divisors, excluding itself.

Step 2: Use the Euclidean Formula

  • Familiarize yourself with the Euclidean formula for generating perfect numbers: 2(p-1)(2p-1) is a prime number, also known as a Mersenne prime.

Step 3: Identify Mersenne Primes

  • Search for Mersenne primes, which are prime numbers that can be expressed as 2p-1 also being a prime number.

Step 4: Apply the Formula

  • For each Mersenne prime you find, apply the Euclidean formula 2(p-1)(2p-1) to calculate a perfect number.

Step 5: Verify the Perfect Number

  • To ensure the number is perfect, verify that the sum of its proper divisors equals the number itself. This can be done by listing all divisors of the number, excluding the number, and adding them up.


  • Step 1: Choose a prime number, such as p = 2
  • Step 2: Calculate 2(p-1) = 2(2) -1 = 3 which is a Mersenne prime.
  • Step 3: Apply the formula to get 2(2-1) (22-1) = 21 * 3 = 6 .
  • Step 4: Verify that 6 is perfect since its divisors (1, 2, 3) sum up to 6.

By following these steps, you can find perfect numbers and explore the fascinating world of number theory.

Perfect Numbers List

Perfect Numbers List

Here’s a table listing some of the known perfect numbers, showcasing their rarity and the pattern that they are all even:

Perfect Number Sum of Divisors excluding itself
6 1 + 2 + 3 = 6
28 1 + 2 + 4 + 7 + 14 = 28
496 1 + 2 + 4 + 8 + 16 + 31 + 62 + 124 + 248 = 496
8128 1 + 2 + 4 + 8 + 16 + 32 + 64 + 127 + 254 + 508 + 1016 + 2032 + 4064 = 8128
33550336 Sum of its proper divisors equals 33550336

These examples illustrate the exponential growth in the size of perfect numbers as they increase, highlighting their unique mathematical beauty.

Theorem of Even Perfect Numbers

The theorem concerning even perfect numbers states that every even perfect number is of the form (2(p-1)(2p-1), where 2p-1 is a prime number, also known as a Mersenne prime. This relationship was first documented by Euclid in his work, “Elements,” establishing a fundamental link between even perfect numbers and Mersenne primes. The theorem implies that the search for even perfect numbers can be directly associated with the search for Mersenne primes. Since all known perfect numbers are even, this theorem is crucial for understanding their structure and guides mathematicians in the search for new perfect numbers. Notably, no odd perfect numbers have been discovered, leading to the conjecture that all perfect numbers may indeed be even, a hypothesis that remains unproven to this day.

Perfect Numbers From 1 to 100

Perfect Numbers Examples

In the range from 1 to 100, there is only one perfect number: 6. It uniquely qualifies as a perfect number because it equals the sum of its divisors (excluding itself), which are 1, 2, and 3. The equation is straightforward: 1 + 2 + 3 = 6.

Facts about Perfect Numbers

    1. Ancient Origins: The concept of perfect numbers dates back to ancient Greek mathematics, with Euclid’s “Elements” providing the first known definition and method for finding them.
    2. Rare Finds: Perfect numbers are extremely rare. As numbers grow larger, the frequency of perfect numbers decreases, making each discovery significant in the mathematical community.
    3. Even Nature: All known perfect numbers are even. This is because they are generated using Euclid’s formula, which inherently produces even numbers.
    4. Mersenne Connection: Every perfect number discovered so far is associated with Mersenne primes through the formula 2p-1 (2p-1), 2p-1 where  is a Mersenne prime
    5. Unsolved Mystery: It remains unknown whether any odd perfect numbers exist, as none have been found and no proof has been established to rule out their possibility.
    6. Infinite Search: Mathematicians have not yet determined if there are infinitely many perfect numbers, making it one of the longstanding open questions in number theory.
    7. Applications: Beyond their mathematical beauty, perfect numbers have applications in cryptography, digital error detection, and the organization of data structures.

These facts highlight the enduring intrigue and complexity of perfect numbers, underscoring their special place in the history and ongoing exploration of mathematics.

Solved Examples

1: Verifying a Perfect Number

Question: Verify if 28 is a perfect number.


  • First, identify the divisors of 28, excluding itself: 1, 2, 4, 7, 14.
  • Next, sum these divisors: 1 + 2 + 4 + 7 + 14 = 28.
  • Since the sum of its divisors equals the number itself, 28 is a perfect number.

2: Finding a Perfect Number Using Euclid’s Formula

Question: Use Euclid’s formula to find a perfect number, given that 2p is a prime number.


  • Euclid’s formula is (2p-1)(2p-1) for p =2, 2p, which is prime.
  • Apply the formula: .
  • Thus, using Euclid’s formula with, we find that 6 is a perfect number.

3: Identifying Non-Perfect Number

Question: Is 10 a perfect number?


  • Determine the divisors of 10, excluding itself: 1, 2, 5.
  • Sum these divisors: 1 + 2 + 5 = 8.
  • Since the sum (8) does not equal the number itself (10), 10 is not a perfect number.

4: Using Euclid’s Formula for Larger Prime

Question: Find a perfect number using 23as part of Euclid’s formula.


  • Given p =3, 23, a prime number.
  • Applying Euclid’s formula: 23-1 (23-1) = 22*7 = 4*7=28.
  • Therefore, 28 is a perfect number found using a larger prime within Euclid’s formula.

5: Exploring Higher Perfect Number

Question: Confirm if 496 is a perfect number.


  • First, list the divisors of 496, excluding itself: 1, 2, 4, 8, 16, 31, 62, 124, 248.
  • Summing these divisors: 1 + 2 + 4 + 8 + 16 + 31 + 62 + 124 + 248 = 496.
  • Since the sum of its divisors equals 496, it is confirmed as a perfect number.

These examples illustrate the methodology for verifying, finding, and understanding perfect numbers, highlighting their unique property of being equal to the sum of their proper divisors.

In conclusion, perfect numbers represent a fascinating intersection of mathematics and mystique, embodying harmony and balance within number theory. Through the exploration of perfect numbers, from ancient formulas to modern computational methods, we uncover the elegance inherent in mathematics. This article has aimed to demystify these rare numerical gems, providing educators and students with insights to appreciate the profound beauty and order of the mathematical world.

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History of Perfect Numbers

Perfect Numbers List in a Table