256665985 has 4 divisors (see below), whose sum is σ = 307999188. Its totient is φ = 205332784.

The previous prime is 256665971. The next prime is 256666031. The reversal of 256665985 is 589566652.

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 178944129 + 77721856 = 13377^2 + 8816^2 .

It is a cyclic number.

It is not a de Polignac number, because 256665985 - 2¹¹ = 256663937 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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, 25666594 + ... + 25666603.

It is an arithmetic number, because the mean of its divisors is an integer number (76999797).

Almost surely, 2^256665985 is an apocalyptic number.

It is an amenable number.

256665985 is a deficient number, since it is larger than the sum of its proper divisors (51333203).

256665985 is an equidigital number, since it uses as much as digits as its factorization.

256665985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51333202.

The product of its digits is 3888000, while the sum is 52.

The square root of 256665985 is about 16020.7985131828. The cubic root of 256665985 is about 635.5105613368.

The spelling of 256665985 in words is "two hundred fifty-six million, six hundred sixty-five thousand, nine hundred eighty-five".