257 (number)
Encyclopedia
257 is the natural number between 256
and 258. It is also a prime number
.
of the form
and therefore a Fermat prime. It is currently the second largest known Fermat prime. It is also a Proth prime. And since it is of the form 4n + 1, it is a Pythagorean prime
.
It is also an irregular prime, and a long prime (in base 10) and a balanced prime. Since the next prime, 263, is 6 away, 257 is called a sexy prime
.
Since 257 + 2 = 259, a semiprime, 257 is a Chen prime
. It is also an Eisenstein prime
with no imaginary part, and a Pierpont prime
.
. See List of country calling codes.
256 (number)
256 is the natural number following 255 and preceding 257.-In mathematics:256 is a composite number, with the factorization 256 = 28, which makes it a power of two....
and 258. It is also a prime number
Prime number
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number. For example 5 is prime, as only 1 and 5 divide it, whereas 6 is composite, since it has the divisors 2...
.
In mathematics
257 is a prime numberPrime number
A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number. For example 5 is prime, as only 1 and 5 divide it, whereas 6 is composite, since it has the divisors 2...
of the form
and therefore a Fermat prime. It is currently the second largest known Fermat prime. It is also a Proth prime. And since it is of the form 4n + 1, it is a Pythagorean primePythagorean prime
A Pythagorean prime is prime number of the form 4n + 1. These are exactly the primes that can be the hypotenuse of a Pythagorean triangle.The first few Pythagorean primes are...
.
It is also an irregular prime, and a long prime (in base 10) and a balanced prime. Since the next prime, 263, is 6 away, 257 is called a sexy prime
Sexy prime
In mathematics, a sexy prime is a prime number that differs from another prime number by six. For example, the numbers 5 and 11 are both sexy primes, because they differ by 6...
.
Since 257 + 2 = 259, a semiprime, 257 is a Chen prime
Chen prime
A prime number p is called a Chen prime if p + 2 is either a prime or a product of two primes. The even number 2p + 2 therefore satisfies Chen's theorem....
. It is also an Eisenstein prime
Eisenstein prime
In mathematics, an Eisenstein prime is an Eisenstein integerz = a + b\,\omega\qquadthat is irreducible in the ring-theoretic sense: its only Eisenstein divisors are the units , a + bω itself and its associates.The associates and the complex conjugate...
with no imaginary part, and a Pierpont prime
Pierpont prime
A Pierpont prime is a prime number of the form2^u 3^v + 1\,for some nonnegative integers u and v. They are named after the mathematician James Pierpont....
.
In other fields
257 is the country calling code for BurundiBurundi
Burundi , officially the Republic of Burundi , is a landlocked country in the Great Lakes region of Eastern Africa bordered by Rwanda to the north, Tanzania to the east and south, and the Democratic Republic of the Congo to the west. Its capital is Bujumbura...
. See List of country calling codes.