256881391 has 16 divisors (see below), whose sum is σ = 286896960. Its totient is φ = 228372480.

The previous prime is 256881389. The next prime is 256881397. The reversal of 256881391 is 193188652.

It is a cyclic number.

It is not a de Polignac number, because 256881391 - 2¹ = 256881389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256881397) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 241126 + ... + 242188.

It is an arithmetic number, because the mean of its divisors is an integer number (17931060).

Almost surely, 2^256881391 is an apocalyptic number.

256881391 is a deficient number, since it is larger than the sum of its proper divisors (30015569).

256881391 is a wasteful number, since it uses less digits than its factorization.

256881391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1746.

The product of its digits is 103680, while the sum is 43.

The square root of 256881391 is about 16027.5198018907. The cubic root of 256881391 is about 635.6882949390.

The spelling of 256881391 in words is "two hundred fifty-six million, eight hundred eighty-one thousand, three hundred ninety-one".