Q: What mersenne primes aren't prime?

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Let p = any prime number. (2p -1) is called a Mersenne number. Any such number that is prime is called a Mersenne Prime. Father Mersenne wrote a list of numbers of this type which he thought were prime, but a few were not. In fact, most of the large Mersenne numbers are not prime, but all the really large numbers that have been proved to be prime are Mersenne Primes.

The algorithm for a Mersenne prime is 2n - 1, where n is a prime number and the solution is also a prime number.Applying the Mersenne algorithm to the prime numbers 2, 3, 5, and 7:22 - 1 = 3, 23 - 1 = 7, 25 - 1 = 31, and 27 - 1 = 127.3, 7, 32, and 127 all being prime numbers, this demonstrates the 2, 3, 5, and 7 are all Mersenne primes.

Their are many ways one that some times works is test those answers if prime are Mersenne primes. Or you could google"Is (put the questionable number here)prime?"

A Mersenne Prime is when 2^n-1 is prime. Some examples of a Mersenne Prime are n=2,3,5,7,13,17,19,31,61,89,107, and 127The first forty Mersenne primes are 2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, 110503, 132049, 216091, 756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917, and 20996011.

1992 is not a Mersenne prime. 1992 is a composite number, being a multiple of 2.

Related questions

Mersenne primes are mostly of interest as mathematical curios. A Mersenne prime has the form 2n-1. For 2n-1 to be prime, n must also be prime. Perfect numbers have the form 2n-1(2n-1) where 2n-1 is a Mersenne prime, so when a new Mersenne prime is discovered, another perfect number is also found.

Mersenne prime is the largest known prime number

The first four Mersenne primes are 2, 3, 5, and 7.

It is, as of now, an open question whether there are a finite or an infinite number of Mersenne primes. At the beginning of the 21st century there were 47 known Mersenne primes, the highest being 43,112,609.

As of the current date, November 2011, only forty-seven Mersenne primes are known.

There were 47 known Mersenne primes at the beginning of the 21st century, the highest being 43,112,609.

Let p = any prime number. (2p -1) is called a Mersenne number. Any such number that is prime is called a Mersenne Prime. Father Mersenne wrote a list of numbers of this type which he thought were prime, but a few were not. In fact, most of the large Mersenne numbers are not prime, but all the really large numbers that have been proved to be prime are Mersenne Primes.

A Mersenne number is a number that can be written as 2n - 1. A Mersenne prime is a Mersenne number that is a prime number. Here are some Mersenne primes: 22 - 1 = 3 23 - 1 = 7 25 - 1 = 31 27 - 1 = 127

A prime number has only two factors, 1 and itself. A Mersenne prime is a prime number derived from the algorithm 2n - 1. For example, 23 - 1 = 7 and 7 is a prime number so 3 is a Mersenne prime. Similarly 27 - 1 = 127 and 127 is a prime number so 7 is a Mersenne prime. There are 47 known Mersenne primes, the highest being 43,112,609.

The algorithm for a Mersenne prime is 2n - 1, where n is a prime number and the solution is also a prime number.Applying the Mersenne algorithm to the prime numbers 2, 3, 5, and 7:22 - 1 = 3, 23 - 1 = 7, 25 - 1 = 31, and 27 - 1 = 127.3, 7, 32, and 127 all being prime numbers, this demonstrates the 2, 3, 5, and 7 are all Mersenne primes.

199 is not a Mersenne prime because it does not fit the algorithm 2n - 1. 2199 - 1 = does not produce a prime number. The Mersenne primes below 200 are 2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, and 127.

Mersenne primes are the primes of the form 2^p-1 where p is a prime. These start 2^2-1 = 3, 2^3-1 = 7, 2^5-1 = 31.