256565 has 12 divisors (see below), whose sum is σ = 325164. Its totient is φ = 194304.

The previous prime is 256561. The next prime is 256567. The reversal of 256565 is 565652.

It can be written as a sum of positive squares in 2 ways, for example, as 103684 + 152881 = 322^2 + 391^2 .

It is not a de Polignac number, because 256565 - 2² = 256561 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

Its product of digits (9000) is a multiple of the sum of its prime divisors (125).

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 256565.

It is not an unprimeable number, because it can be changed into a prime (256561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2597 + ... + 2693.

It is an arithmetic number, because the mean of its divisors is an integer number (27097).

2²⁵⁶⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

256565 is a deficient number, since it is larger than the sum of its proper divisors (68599).

256565 is an equidigital number, since it uses as much as digits as its factorization.

256565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148 (or 125 counting only the distinct ones).

The product of its digits is 9000, while the sum is 29.

The square root of 256565 is about 506.5224575475. The cubic root of 256565 is about 63.5427203385.

The spelling of 256565 in words is "two hundred fifty-six thousand, five hundred sixty-five".