**What are prime numbers?** Prime numbers are a fundamental concept in mathematics that has intrigued mathematicians for centuries. These unique numbers have a special place in number theory and play a crucial role in various mathematical fields, such as cryptography and coding theory. But what exactly are prime numbers? How are they calculated? And why are they so important? In this article, we will explore the world of prime numbers, their properties, and some interesting examples.

## Introduction to Prime Numbers

### Definition of Prime Numbers

A prime number is a whole number greater than 1 that is only divisible by 1 and itself. In other words, it is a number that has exactly two factors – 1 and itself. For example, 7 is a prime number because its only factors are 1 and 7. On the other hand, 8 is not a prime number because it has more than two factors – 1, 2, 4, and 8.

Prime numbers are considered the building blocks of all other numbers as every integer can be expressed as a product of primes. This idea forms the basis of a fundamental theorem in arithmetic, known as the Fundamental Theorem of Arithmetic.

### Basic Properties of Prime Numbers

Before we dive into the table of prime numbers and example problems, let’s go over some basic properties of prime numbers:

- 1 is not a prime number. This is because 1 has only one factor, which is itself.
- All prime numbers except 2 are odd. This is because even numbers have more than two factors, as they are divisible by 2.
- The set of prime numbers is infinite. This means that there is no highest or largest prime number. There will always be a bigger prime number.
- The smallest divisor of any natural number is a prime number. This follows from the definition of prime numbers – a number can only be divided by 1 and itself, making it the smallest divisor.
- A number X is a prime number if its smallest divisor (other than 1) is smaller than the square root of X. This is a useful property when determining if a number is prime or not.

## Prime Number Table

Now that we have a better understanding of prime numbers and their properties, let’s take a look at a table of prime numbers less than 1000.

Number | Prime? |
---|---|

1 | No |

2 | Yes |

3 | Yes |

4 | No |

5 | Yes |

6 | No |

7 | Yes |

8 | No |

9 | No |

10 | No |

11 | Yes |

12 | No |

13 | Yes |

14 | No |

15 | No |

16 | No |

17 | Yes |

18 | No |

19 | Yes |

20 | No |

21 | No |

22 | No |

23 | Yes |

24 | No |

25 | No |

26 | No |

27 | No |

28 | No |

29 | Yes |

30 | No |

31 | Yes |

32 | No |

33 | No |

34 | No |

35 | No |

36 | No |

37 | Yes |

38 | No |

39 | No |

40 | No |

41 | Yes |

42 | No |

43 | Yes |

44 | No |

45 | No |

46 | No |

47 | Yes |

48 | No |

49 | No |

50 | No |

51 | No |

52 | No |

53 | Yes |

54 | No |

55 | No |

56 | No |

57 | No |

58 | No |

59 | Yes |

60 | No |

61 | Yes |

62 | No |

63 | No |

64 | No |

65 | No |

66 | No |

67 | Yes |

68 | No |

69 | No |

70 | No |

71 | Yes |

72 | No |

73 | Yes |

74 | No |

75 | No |

76 | No |

77 | No |

78 | No |

79 | Yes |

80 | No |

81 | No |

82 | No |

83 | Yes |

84 | No |

85 | No |

86 | No |

87 | No |

88 | No |

89 | Yes |

90 | No |

91 | No |

92 | No |

93 | No |

94 | No |

95 | No |

96 | No |

97 | Yes |

98 | No |

99 | No |

100 | No |

From this table, we can see that there are 168 prime numbers less than 1000. This may seem like a small number compared to the total number of integers in this range, but as we go higher, the percentage of primes decreases.

## Example Problems

Now that we have a better understanding of prime numbers and have seen a table of them, let’s try some example problems involving primes.

### Prime Factorization

Breaking a number down into its prime factors is an essential skill in mathematics. It involves finding all the prime numbers that can divide a given number without leaving a remainder.

For example, let’s find the prime factorization of 72.

Step 1: Divide by the smallest prime number possible, which is 2.

72 ÷ 2 = 36. So, the first factor is 2.

Step 2: Now, divide 36 by 2 again.

36 ÷ 2 = 18. So, the second factor is also 2.

Step 3: Continue dividing by 2 until we can no longer divide evenly.

18 ÷ 2 = 9 9 ÷ 2 = not a whole number

So, the next factor is 3.

Step 4: Divide by 3.

9 ÷ 3 = 3

We can stop here as 3 is already a prime number.

Therefore, the prime factorization of 72 is 2 x 2 x 2 x 3 x 3.

### Finding the Greatest Common Divisor (GCD)

The greatest common divisor (GCD) of two numbers is the largest number that divides both of them evenly. To find the GCD, we can use the prime factorization method.

For example, let’s find the GCD of 24 and 36.

Step 1: Find the prime factorization of 24 and 36.

24 = 2 x 2 x 2 x 3 36 = 2 x 2 x 3 x 3

Step 2: Identify the common prime factors.

Common factors: 2 x 2 x 3

Step 3: Multiply the common factors to get the GCD.

GCD = 2 x 2 x 3 = 12

Therefore, the GCD of 24 and 36 is 12.

## Other Definitions

Apart from the basic properties and table of prime numbers, there are a few other definitions related to primes that are worth mentioning.

### Relatively Prime Numbers

Two numbers are relatively prime if their greatest common divisor is 1. In other words, they have no common factors except for 1. For example, 15 and 28 are relatively prime because their only common factor is 1.

Relatively prime numbers play an important role in various areas of mathematics, such as group theory and number theory.

### Super Prime Numbers

Super prime numbers are a special type of prime number that remains prime even after adding digits to either side. For example, 31 is a super prime because 131, 313, and 3131 are also prime numbers.

Interestingly, the only two-digit super prime number is 23, and there are only four three-digit super primes – 113, 311, 337, and 373.

## 1 and 2: Special Cases

In the introduction, it was mentioned that 1 is not considered a prime number. This is because of some unique properties that make 1 different from other prime numbers.

### 1:

Although 1 has only one factor – itself, it is not considered a prime number. This is because every prime number must have exactly two distinct factors. Since 1 does not meet this criterion, it is not classified as a prime number.

### 2:

On the other hand, 2 is considered a prime number, even though it is technically the only even prime number. This is because it satisfies all the criteria for being a prime number – it has exactly two factors (1 and 2), it is divisible only by 1 and itself, and it is the smallest prime number.

## Conclusion

Prime numbers are fascinating and play a crucial role in mathematics. They have been studied for centuries, and yet, there is still much to discover about them. In this article, we have explored the definition and basic properties of prime numbers, seen a table of prime numbers, and tried some example problems. We have also discussed other definitions related to primes and looked at the special cases of 1 and 2. Hopefully, this article has given you a better understanding of prime numbers and sparked your curiosity to learn more about them.