256609391 has 2 divisors, whose sum is σ = 256609392. Its totient is φ = 256609390.

The previous prime is 256609333. The next prime is 256609417. The reversal of 256609391 is 193906652.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256609391 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256609291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128304695 + 128304696.

It is an arithmetic number, because the mean of its divisors is an integer number (128304696).

Almost surely, 2^256609391 is an apocalyptic number.

256609391 is a deficient number, since it is larger than the sum of its proper divisors (1).

256609391 is an equidigital number, since it uses as much as digits as its factorization.

256609391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 87480, while the sum is 41.

The square root of 256609391 is about 16019.0321492904. The cubic root of 256609391 is about 635.4638485783.

The spelling of 256609391 in words is "two hundred fifty-six million, six hundred nine thousand, three hundred ninety-one".