256000391 has 2 divisors, whose sum is σ = 256000392. Its totient is φ = 256000390.

The previous prime is 256000361. The next prime is 256000403. The reversal of 256000391 is 193000652.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256000391 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 256000391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256000321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128000195 + 128000196.

It is an arithmetic number, because the mean of its divisors is an integer number (128000196).

Almost surely, 2^256000391 is an apocalyptic number.

256000391 is a deficient number, since it is larger than the sum of its proper divisors (1).

256000391 is an equidigital number, since it uses as much as digits as its factorization.

256000391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1620, while the sum is 26.

The square root of 256000391 is about 16000.0122187453. The cubic root of 256000391 is about 634.9607440547.

The spelling of 256000391 in words is "two hundred fifty-six million, three hundred ninety-one", and thus it is an aban number.