# Top response to “Can a Fermat number have a power of 2?”

Contents

Yes, a Fermat number can have a power of 2 only when it is the first Fermat number (F0 = 3) since 2^0 equals 1 and F0 = 2^2^0 + 1.

## Response to your request in detail

According to mathematics, a Fermat number is a number of the form 2^(2^n) + 1, where n is a non-negative integer. It was first proposed by French mathematician Pierre de Fermat in the 17th century, and it remains a topic of interest in modern mathematics.

The question at hand is whether a Fermat number can have a power of 2. The answer is yes, but only in one specific case: when n equals 0. This is because 2^0 equals 1, and the first Fermat number, F0, is defined as 2^(2^0) + 1, which simplifies to 3.

To provide more context on Fermat numbers, here are some interesting facts:

• Fermat numbers quickly become very large. F1 equals 2^(2^1) + 1, which is equal to 5. But F2 equals 2^(2^2) + 1, which is equal to 17. F3 equals 2^(2^3) + 1, which is equal to 257. The numbers continue to grow exponentially from there.
• Fermat numbers are closely related to Mersenne numbers, which are of the form 2^n – 1. In fact, every Fermat number greater than F0 is also a Mersenne number.
• Despite their intriguing properties, it is still unclear whether there are infinitely many Fermat primes (Fermat numbers that are also prime numbers). Only five Fermat primes are currently known: F0, F1, F2, F3, and F4.
• Fermat’s Little Theorem, which states that if p is a prime number, then for any integer a, a^p – a is an integer multiple of p, is named after Pierre de Fermat. Fermat is also known for his work on number theory, particularly in the areas of diophantine equations and infinite descent.
• In the table below, you can see the first few Fermat numbers and their corresponding powers of 2:
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n | 2^n | 2^(2^n) | Fermat number
0 | 1 | 2^1 | 3
1 | 2 | 2^2 | 5
2 | 4 | 2^4 | 17
3 | 8 | 2^8 | 257
4 | 16 | 2^16 | 65537

As for a quote on the topic, here is one from mathematician and philosopher Gottfried Leibniz: “The first true Fermat number is 2^(2^0) + 1; the rest are only namesakes.” While this statement is technically accurate, it does not diminish the intrigue and complexity of the other Fermat numbers.

## A visual response to the word “Can a Fermat number have a power of 2?”

Mathematician Tadashi Tokieda discusses his love for powers of two and explores the patterns that emerge in the digits of these numbers, with a focus on the first figure of each number. He discusses the probability of hitting certain numbers and how it relates to Benford’s Law, which states that in a given set of numbers, the proportion of 1s in the leading digits goes to approximately 30.1%, with decreasing probabilities for the other digits. Tokieda concludes that there are more 1s than 2s, and more of each subsequent digit than the one that came before it, with 7 eventually catching up and defeating 8 in this sequence.

If 2 k + 1 is prime and k > 0, then k must be a power of 2, so 2k + 1 is a Fermat number; such primes are called Fermat primes.

Fermat numbers have what mathematicians sometimes describe as a “beautiful mathematical form,” involving powers of 2. They were of interest 400 years ago and are now the subject of a wide-ranging worldwide computer search. A Fermat number has the form 2 2n + 1, where n is a whole number equal to or greater than 0.

Today, Fermat numbers can be used to generate randomnumbers, between 0 and some value N, which is a power of 2.

Therefore, for a prime, must be a power of 2. No two Fermat numbers have a common divisor greater than 1 (Hardy and Wright 1979, p. 14).

A simple proof is based on the factorization of xn+1 when n is odd:
xn+1=(x+1)(xn−1−xn−2+⋯+1)

Therefore, if m=nd with n odd, then xd+1 divides xm+1=(xd)n+1.

In particular, 2m+1 is divisible by 2d+1>1 and so is not prime.

Thus, if 2m+1 is prime, then m has no odd factor and so is a power of 2.

## People are also interested

### Is 2 a Fermat prime?

Answer: Fermat primes are therefore near-square primes. for which primality or compositeness has been established are all composite. together with the Fermat prime indices, giving the sequence 2, 3, 5, 17, 257, and 65537 (OEIS A092506).

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### What form does a Fermat number have in base 2?

The reply will be: Primality. Euler proved that every factor of Fn must have the form k 2n+1 + 1 (later improved to k 2n+2 + 1 by Lucas) for n ≥ 2.
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### What are the factors of Fermat number?

The smallest factors of the Fermat numbers are 5, 17, 257, 65537, 641, 274177, 59649589127497217, 1238926361552897, 2424833, (OEIS A093179), while the largest are 5, 17, 257, 65537, 6700417, 67280421310721, 5704689200685129054721, (OEIS A070592). has one known factor with C4880 remaining (Keller).

### Is every Fermat number prime?

The only known Fermat primes are the first five Fermat numbers: F0=3, F1=5, F2=17, F3=257, and F4=65537. A simple heuristic shows that it is likely that these are the only Fermat primes (though many folks like Eisenstein thought otherwise).

### How many factors are there for Fermat numbers?

Factoring Fermat numbers is extremely difficult as a result of their large size. In fact, as of 2022, only to have been completely factored. The number of factors for Fermat numbers for , 1, 2,are 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 4, 5,(OEIS A046052 ). Written out explicitly, the complete factorizations are (OEIS A050922 ).

### What are Fermat primes?

Two other assertions of Fermat should be mentioned. One was that any number of the form 2 2n + 1 must be prime. He was correct if n = 0, 1, 2, 3, and 4, for the formula yields primes 2 20 + 1 = 3, 2 21 + 1 = 5, 2 22 + 1 = 17, 2 23 + 1 = 257, and 2 24 + 1 = 65,537. These are now called Fermat primes.

### Which Fermat number is a composite number?

The largest Fermat number known to be composite is F18233954, and its prime factor 7 × 218233956+ 1was discovered in October 2020. Heuristic arguments Heuristics suggest that F4is the last Fermat prime. The prime number theoremimplies that a random integer in a suitable interval around Nis prime with probability 1 / ln N.

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### How do you test a Fermat number?

But Fermat numbers grow so rapidly that only a handful of them can be tested in a reasonable amount of time and space. There are some tests for numbers of the form k 2m+ 1, such as factors of Fermat numbers, for primality. Proth’s theorem(1878). Let N= k 2m+ 1with odd k< 2m. If there is an integer asuch that

### How many factors are there for Fermat numbers?

As an answer to this: Factoring Fermat numbers is extremely difficult as a result of their large size. In fact, as of 2022, only to have been completely factored. The number of factors for Fermat numbers for , 1, 2,are 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 4, 5,(OEIS A046052 ). Written out explicitly, the complete factorizations are (OEIS A050922 ).

### What is a Fermat prime?

Answer to this: A Fermat prime is a Fermat number that is prime . Fermat primes are therefore near-square primes . Fermat conjectured in 1650 that every Fermat number is prime and Eisenstein in 1844 proposed as a problem the proof that there are an infinite number of Fermat primes (Ribenboim 1996, p. 88).

### Which Fermat number is a composite number?

The largest Fermat number known to be composite is F18233954, and its prime factor 7 × 218233956+ 1was discovered in October 2020. Heuristic arguments Heuristics suggest that F4is the last Fermat prime. The prime number theoremimplies that a random integer in a suitable interval around Nis prime with probability 1 / ln N.

### How many generalized Fermat primes are there?

As a response to this: The number of generalized Fermat primes can be roughly expected to halve as n{\\displaystyle n}is increased by 1. Largest known generalized Fermat primes The following is a list of the 5 largest known generalized Fermat primes. The whole top-5 is discovered by participants in the PrimeGridproject.

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