256985681 has 4 divisors (see below), whose sum is σ = 257047092. Its totient is φ = 256924272.

The previous prime is 256985639. The next prime is 256985717. The reversal of 256985681 is 186589652.

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 12845056 + 244140625 = 3584^2 + 15625^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256985681 is a prime.

It is a super-2 number, since 2×256985681² = 132083280478067522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256985081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23930 + ... + 32963.

It is an arithmetic number, because the mean of its divisors is an integer number (64261773).

Almost surely, 2^256985681 is an apocalyptic number.

It is an amenable number.

256985681 is a deficient number, since it is larger than the sum of its proper divisors (61411).

256985681 is an equidigital number, since it uses as much as digits as its factorization.

256985681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61410.

The product of its digits is 1036800, while the sum is 50.

The square root of 256985681 is about 16030.7729383208. The cubic root of 256985681 is about 635.7743099442.

The spelling of 256985681 in words is "two hundred fifty-six million, nine hundred eighty-five thousand, six hundred eighty-one".