256810391 has 2 divisors, whose sum is σ = 256810392. Its totient is φ = 256810390.

The previous prime is 256810361. The next prime is 256810439. The reversal of 256810391 is 193018652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256810391 - 2¹⁸ = 256548247 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256810361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128405195 + 128405196.

It is an arithmetic number, because the mean of its divisors is an integer number (128405196).

Almost surely, 2^256810391 is an apocalyptic number.

256810391 is a deficient number, since it is larger than the sum of its proper divisors (1).

256810391 is an equidigital number, since it uses as much as digits as its factorization.

256810391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 35.

The square root of 256810391 is about 16025.3047084915. The cubic root of 256810391 is about 635.6297231242.

The spelling of 256810391 in words is "two hundred fifty-six million, eight hundred ten thousand, three hundred ninety-one".