256009865 has 4 divisors (see below), whose sum is σ = 307211844. Its totient is φ = 204807888.

The previous prime is 256009861. The next prime is 256009877. The reversal of 256009865 is 568900652.

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 107267449 + 148742416 = 10357^2 + 12196^2 .

It is a cyclic number.

It is not a de Polignac number, because 256009865 - 2² = 256009861 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256009861) 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, 25600982 + ... + 25600991.

It is an arithmetic number, because the mean of its divisors is an integer number (76802961).

Almost surely, 2^256009865 is an apocalyptic number.

It is an amenable number.

256009865 is a deficient number, since it is larger than the sum of its proper divisors (51201979).

256009865 is an equidigital number, since it uses as much as digits as its factorization.

256009865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51201978.

The product of its (nonzero) digits is 129600, while the sum is 41.

The square root of 256009865 is about 16000.3082782801. The cubic root of 256009865 is about 634.9685767822.

The spelling of 256009865 in words is "two hundred fifty-six million, nine thousand, eight hundred sixty-five".