# How do I prove Fermat numbers are coprime?

## How do I prove Fermat numbers are coprime?

Any two distinct Fermat numbers Φm and Φn with m>n are relatively prime. Proof. Let Φm and Φn be distinct Fermat numbers with m > n, and suppose that d > 0 is a common divisor of Φm and Φn, then d divides 2 = Φm − Φ0 · Φ1 ··· Φn ··· Φm−1. Therefore, d = 1 or d = 2, but Φm and Φn are odd, so we must have d = 1.

## What is meant by a Fermat number?

In mathematics, a Fermat number, named after Pierre de Fermat, who first studied them, is a positive integer of the form. where n is a non-negative integer. The first few Fermat numbers are: 3, 5, 17, 257, 65537, 4294967297, 18446744073709551617, (sequence A000215 in the OEIS).

Are Fermat numbers square free?

It has been conjectured that the Fermat and Mersenne numbers are all square-free. In this note it is shown that if some Fermat or Mersenne number fails to be square-free, then for any prime p whose square divides the appropriate number, it must be that 2P”1 = 1 (mod p2).

### How did Euler disprove Fermat?

Fermat conjectured that all Fermat numbers are prime. (Unlike Fermat’s Last Theorem, he never claimed to have a proof of this one.) In 1732, about 70 years after Fermat’s death, Leonhard Euler factored the 5th Fermat number into 641×6,700,417, disproving Fermat’s conjecture.

### What is this number 4294967296?

4294967296 is the 65536-th square number. 4294967296 is a deficient number, since it is larger than the sum of its proper divisors (4294967295). 4294967296 is an frugal number, since it uses more digits than its factorization. 4294967296 is an odious number, because the sum of its binary digits is odd.

Are there only 5 Fermat primes?

So we call these the Fermat numbers, and when a number of this form is prime, we call it a Fermat prime. The only known Fermat primes are the first five Fermat numbers: F0=3, F1=5, F2=17, F3=257, and F4=65537.

## What is a Fermat prime number?

See below for a complete proof.) In other words, every prime of the form 2 k + 1 (other than 2 = 2 0 + 1) is a Fermat number, and such primes are called Fermat primes. As of 2019, the only known Fermat primes are F0, F1, F2, F3, and F4 (sequence A019434 in the OEIS ).

## What is the largest Fermat number known to be composite?

The largest Fermat number known to be composite is F18233954, and its prime factor 7 × 218233956 + 1, a megaprime, was discovered in October 2020. Heuristics suggest that F4 is the last Fermat prime. The prime number theorem implies that a random integer in a suitable interval around N is prime with probability 1 / ln N.

What is the factorization of Fermat numbers?

Factorization of Fermat numbers F0 2 1 3 is prime F1 2 2 5 is prime F2 2 4 17 is prime F3 2 8 257 is prime F4 2 16 65,537 is the largest known Fermat prime

### What is the last digit of a Fermat number?

No Fermat prime can be expressed as the difference of two p th powers, where p is an odd prime. With the exception of F0 and F1, the last digit of a Fermat number is 7. The sum of the reciprocals of all the Fermat numbers (sequence A051158 in the OEIS) is irrational.