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Twin prime numbers are defined as the set of prime numbers that have exactly one composite number in between them. In other words, we can define these numbers as the prime numbers that have a difference of two between them.
- We can also use the number to describe one of the two twin prime numbers.
- These numbers are either two less or two more than another prime number.
- It is also known as prime twin or prime pair.
- The term was coined by Stackel in 1916.
- They are considered rare when evaluating large-range values.
- It has been determined that there are infinitely many different types of twin primes.
- {3,5}, {5,7}, {11,13} and {17,19} are first set of these numbers.
Key Terms: Prime Numbers, Twin Primes, Prime Triplets, Conjectures, Co-Prime Numbers, Numbers, Prime Gap, First Hardy-Littlewood Conjecture, Twin Prime Number Conjecture, Composite Numbers
Properties of Twin Prime
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Twin prime are prime numbers that have a difference of two between them. These numbers have something in common between them. Numbers that belong to these categories depict some common properties, which are as follows:
- Every twin prime number except (3,5) can be expressed in one given form, which is 6n+1 and 6n-1.
- The sum of every twin prime number except (3,5) can be expressed in the form of 12n as 6n-1) + (6n+1) = 12n.
- Any two prime numbers that do not have a composite number between them cannot be considered as twin prime.
- 5 is the only prime number that has both positive and negative prime gaps.
- It has a negative gap of 2 with 3 and a positive gap of 2 with 7.
- So, it is the only prime number that occurs in two prime twins.
Example of Properties of Twin PrimeExample: For example, the prime numbers (2,3) have no composite number between them. Hence, they cannot be considered as twin primes. |
Twin Prime
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| Polynomials | Quadratic Equations Formula | Degree of polynomial |
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First Few Pairs of Twin Prime
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To find the first few pairs of twin primes, we must look at the prime numbers that occur first. The first set of twin prime numbers are (3,5). The next set of twin prime numbers are (5,7), (11,13), (17,19) etc.
- The next pair of twin prime numbers can be found because they can be expressed in the form of (6n-1, 6n+1).
- All the twin prime numbers can be expressed in the form of (6n-1, 6n+1) except the pair (3,5).
- Further, there are infinite numbers of twin prime numbers that can be found by using this conjecture.
As a result first few pairs of twin prime numbers are as follows:
- (3,5), (5,7), (11,13), (17,19), (29,31), (41,43), (59,61), (71,73), (101,103), (107,109), (137,139), (149,151), (179,181), (197,199)…..
Twin Prime Numbers List
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The twin prime numbers start from (3,5). The list of the twin prime numbers less than 1000 are as follows:
Twin prime numbers from 1 to 50
The number are as follows:
- (3,5), (5,7), (11,13), (17,19), (29,31), (41,43)
Twin prime numbers from 51 to 100
The number are as follows:
- (59,61), (71,73)
Twin prime numbers from 101 to 200
The number are as follows:
- (101,103), (107,109), (137,139), (149,151), (179,181), (197,199)
Twin prime numbers from 201 to 300
The number are as follows:
- (227,229), (239,241), (269,271), (281,283)
Twin prime numbers from 301 to 400
The number are as follows:
- (311,313), (347, 349)
Twin prime numbers from 401 to 500
The number are as follows:
- (419, 421), (431, 433), (461, 463)
Twin prime numbers from 501 to 1000
The number are as follows:
- (521, 523), (569, 571), (599, 601), (617, 619), (641,643), (659, 661), (809, 811), (821,823), (827,829), (857, 859), (881,883).
Prime Gap
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Prime gap is defined as the difference between two consecutive prime numbers. The smallest and only odd prime number is of gap one. As a result, the required number of prime gap of n numbers can occur at much smaller than n!.
- Similarly, the prime gap for other successive prime numbers can be found out by finding the difference between them.
- According to the prime number theorem, the average prime gap between a prime and the next prime will be ln(p).
- As per analysis, the prime gap of 60 numbers is as follows:
{1, 2, 2, 4, 2, 4, 2, 4, 6, 2, 6, 4, 2, 4, 6, 6, 2, 6, 4, 2, 6, 4, 6, 8, 4, 2, 4, 2, 4, 14, 4, 6, 2, 10, 2, 6, 6, 4, 6, 6, 2, 10, 2, 4, 2, 12, 12, 4, 2, 4, 6, 2, 10, 6, 6, 6, 2, 6, 4, 2}
- It can mathematically be represented as follows:
Prime gap = prime number + 1 – prime number
Example of Prime GapExample: For example, 2 and 3 are two successive prime numbers, so the prime gap between them is equal to 1 (3-2=1). |
Prime Triplets
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Prime triplets are a set of three numbers that can be represented in a common factor. The form that is used in expressing the triplets is (n, n+2, n+6) or (n, n+4, n+6).
- In these numbers, the difference between the smallest and largest prime number is six.
- Twin prime, sexy prime and cousin prime are three types of prime triplets.
- One of the numbers in the group is a multiple of three.
- (2, 3, 5) and (3, 5, 7) are two sets of prime triplets.
Conjectures
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Conjectures are divided into two categories which are as follows:
Twin Prime Number Conjecture
Twin prime number conjecture is also known as Polignac’s conjecture in number theory. According to this conjecture, for each positive even number m, there are infinitely many pairs of two consecutive prime numbers with difference n.
- According to this conjecture, there are infinitely many twin primes.
- As the numbers go on increasing, the occurrence of twin prime numbers decreases.
- The term was coined by French mathematician Alphonse de Polignac in 1896.
- He expressed that even can be explained by the difference between two consecutive prime numbers.
Example of Twin Prime Number ConjectureExample: 2 = 5 − 3 = 7 − 5 = 13 − 11 is a set of Twin Prime Number Conjecture |
First Hardy-Littlewood Conjecture
The First Hardy-Littlewood conjecture is an extension of the twin prime number conjecture. It is related to the distribution of prime numbers, including twin primes with respect to the prime number theorem.
- Let p(x) denote the number of primes p<=x, such that p+2 is also prime (twin prime).
- Then the twin prime constant c, is given by C= summation p>=3 (1-1/(p-1)^2.
Difference between Twin Prime and Co-Prime Numbers
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The difference between Twin Prime and Co-Prime Numbers are as follows:
| Twin Prime | Co-Prime Numbers |
|---|---|
| Twin prime numbers are the prime numbers that have a difference of two between them and the number occurring in between them is a composite number. | Co-prime numbers are the numbers that have only one common factor between them, that is 1. Other than 1 there are no other common factors. |
| All the twin prime numbers are co-prime numbers | All the co-prime numbers are not twin prime. |
| 23 and 24 are not twin prime. | 23 and 24 are co-prime numbers as they have only one common factor 1. |
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| Relation Between HCF and LCM | Descending Order | Is '1' a Prime Number? |
| Properties of LCM and HCF | Number Lines | Fundamental Theorem Of Arithmetic |
Things to Remember
- Twin prime numbers are the prime numbers that have a composite number between them, and the difference between them is 2.
- These numbers can be expressed in the form of (6n-1, 6n+1) except (3,5).
- 5 is the only number that has both positive and negative prime gap 2.
- For every positive prime number m, there are an infinite number of twin prime numbers with a difference of n.
- As the numbers increase, the occurrence of twin prime decreases.
- Every twin prime number is co-prime,coprimes but not every coprime is a twin prime.
Sample Questions
Ques: List the first 4 pairs of twin prime numbers. Also list all the twin prime between 1 and 100. Name one number that is the twin prime of two numbers? (2 marks)
Ans: The first 4 pairs of twin prime numbers are (3,5), (5,7), (11,13) and (17,19). All the twin primes between 1 and 100 are (3,5), (5,7), (11,13), (17,19), (29,31), (41,43), (59,61), (71,73). 5 is the number that is the twin prime of both 3 and 7.
Ques: Write one co-prime number and the twin prime number for the following numbers: 3, 101, 61, 881, 857, 461? (2 marks)
Ans: One co-prime and twin prime of the following numbers are given below:
| Co-prime | Twin prime | |
|---|---|---|
| 3 | 4 | 5 |
| 101 | 102 | 103 |
| 61 | 62 | 59 |
| 881 | 880 | 883 |
| 857 | 858 | 859 |
| 461 | 462 | 463 |
Ques: What is the difference between twin prime and co-prime? (2 marks)
Ans: Twin prime numbers are the numbers that have a composite number between them and the difference between them is 2. Co-prime numbers are the numbers that have only 1 as the common factor between them.
Ques: Classify the numbers given below as twin primes and co-primes. (41,43), (11,15), (39,41), (71,73)? (4 marks)
Ans: (41,43): Both the numbers are prime and the difference between them is 2. Also, the number between them is a composite number. So, both are twin primes.
(11,15): Out of these numbers, 15 is not prime and 11 is prime. So, they cannot be twin primes. But they have only one common factor between them i.e., 1. So they are co-primes.
(39,41): 39 is not a prime number. So, the numbers are not twin primes. But both the numbers have only one common factor between them i.e., 1. So they are co-primes.
(71,73): Both the numbers are prime numbers and they have a difference of 2 between them with a composite number between them. So, they are twin primes.
Ques: Prove that the sum of twin prime numbers other than (3,5) are divisible by 12? (3 marks)
Ans: By twin prime conjecture, all the twin prime numbers other than (3,5) can be represented by (6n-1, 6n+1). Let’s consider two prime numbers that are represented by (6k-1, 6k+1). Their sum is 6k-1+6k+1= 12k.
Hence for all the twin prime numbers, their sum can be represented by 12k, where k is any natural number. Now consider (3,5). Their sum is 3+5=8. 8 is not divisible by 12. So the sum of every pair of twin primes other than (3,5) is divisible by 12.
Ques: How many twin prime numbers are there between 100 and 500? (2 marks)
Ans: There are 16 pairs of twin prime numbers between 100 and 500. They are (101, 103), (107, 109), (137,139), (149,151), (179,181), (191,193), (197,199), (227,229), (239, 241), (269,271), (281,283), (311,313), (347,349), (419,421), (431,433), (461,463).
Ques: What are prime triplets? Give some examples. (2 marks)
Ans: The prime triplets are the prime numbers that can be expressed in the form of (n, n+2, n+6) or (n, n+4, n+6). Some examples are (3,5,7), (5,7,11), (7,11,13), (11,13,17), (13,17,19), (17,19,23), (37,41,43), (41,43,47), (67,71,73), (97,101,103), (101,103,107), (103,107,109).
Ques: Write all the twin prime numbers between 500 and 1000? (2 marks)
Ans: All twin prime number between 500 and 1000 is (521, 523), (569,571), (599, 601), (617, 619), (641,643), (659, 661), (809, 811), (821, 823), (827, 829), (857, 859), (881, 883).
Ques: Is 29 a Prime Number or not? (5 marks)
Ans: We can determine this by two methods:
Method 1:
The formula for the prime number is 6n - 1
Let us write the given number in the form of 6n - 1.
6(5) - 1 = 30 - 1 = 19
Method 2:
Check for the factors of 29
29 has only two factors 1 and 29.
Therefore, by both methods, we get 29 as a prime number.
Ques: How many twin prime numbers are there between 400 and 1000? (2 marks)
Ans: There are 14 pairs of twin prime numbers between 100 and 500. They are (419, 421), (431, 433), (461, 463), (521, 523), (569, 571), (599, 601), (617, 619), (641,643), (659, 661), (809, 811), (821,823), (827,829), (857, 859), (881,883).
Ques: Determine whether 1 is a composite or prime number? (2 marks)
Ans: 1 is neither composite nor a prime number. Since 1 can be divided by itself, it has just one factor. It thus contradicts the criteria of both prime and composite numbers. Each of them has more than two components.
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