256961 has 4 divisors (see below), whose sum is σ = 258132. Its totient is φ = 255792.

The previous prime is 256957. The next prime is 256967. The reversal of 256961 is 169652.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 231361 + 25600 = 481^2 + 160^2 .

It is a cyclic number.

It is not a de Polignac number, because 256961 - 2² = 256957 is a prime.

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

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (256967) 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 3 ways as a sum of consecutive naturals, for example, 146 + ... + 731.

It is an arithmetic number, because the mean of its divisors is an integer number (64533).

2²⁵⁶⁹⁶¹ is an apocalyptic number.

256961 is the 293-rd octagonal number.

It is an amenable number.

256961 is a deficient number, since it is larger than the sum of its proper divisors (1171).

256961 is an equidigital number, since it uses as much as digits as its factorization.

256961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1170.

The product of its digits is 3240, while the sum is 29.

The square root of 256961 is about 506.9132075612. The cubic root of 256961 is about 63.5753955959.

It can be divided in two parts, 256 and 961, that multiplied together give a square (246016 = 496²).

The spelling of 256961 in words is "two hundred fifty-six thousand, nine hundred sixty-one".