256388281 has 4 divisors (see below), whose sum is σ = 263317732. Its totient is φ = 249458832.

The previous prime is 256388269. The next prime is 256388309. The reversal of 256388281 is 182883652.

256388281 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 240746256 + 15642025 = 15516^2 + 3955^2 .

It is a cyclic number.

It is not a de Polignac number, because 256388281 - 2²⁷ = 122170553 is a prime.

It is a super-2 number, since 2×256388281² = 131469901268269922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256388381) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3464670 + ... + 3464743.

It is an arithmetic number, because the mean of its divisors is an integer number (65829433).

Almost surely, 2^256388281 is an apocalyptic number.

It is an amenable number.

256388281 is a deficient number, since it is larger than the sum of its proper divisors (6929451).

256388281 is an equidigital number, since it uses as much as digits as its factorization.

256388281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6929450.

The product of its digits is 184320, while the sum is 43.

The square root of 256388281 is about 16012.1291838406. The cubic root of 256388281 is about 635.2812782433.

The spelling of 256388281 in words is "two hundred fifty-six million, three hundred eighty-eight thousand, two hundred eighty-one".