256689 has 10 divisors (see below), whose sum is σ = 383570. Its totient is φ = 171072.

The previous prime is 256687. The next prime is 256699. The reversal of 256689 is 986652.

It can be written as a sum of positive squares in only one way, i.e., 245025 + 11664 = 495^2 + 108^2 .

It is not a de Polignac number, because 256689 - 2¹ = 256687 is a prime.

It is a Duffinian number.

It is a plaindrome in base 10.

It is a nialpdrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (256687) 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 9 ways as a sum of consecutive naturals, for example, 1504 + ... + 1665.

It is an arithmetic number, because the mean of its divisors is an integer number (38357).

2²⁵⁶⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

256689 is a deficient number, since it is larger than the sum of its proper divisors (126881).

256689 is an equidigital number, since it uses as much as digits as its factorization.

256689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3181 (or 3172 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 256689 is about 506.6448460214. The cubic root of 256689 is about 63.5529555983.

The spelling of 256689 in words is "two hundred fifty-six thousand, six hundred eighty-nine".