256840 has 16 divisors (see below), whose sum is σ = 577980. Its totient is φ = 102720.

The previous prime is 256831. The next prime is 256873. The reversal of 256840 is 48652.

It can be written as a sum of positive squares in 2 ways, for example, as 248004 + 8836 = 498^2 + 94^2 .

It is a nialpdrome in base 8.

It is an unprimeable number.

256840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3171 + ... + 3250.

2²⁵⁶⁸⁴⁰ is an apocalyptic number.

256840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

256840 is an abundant number, since it is smaller than the sum of its proper divisors (321140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

256840 is a wasteful number, since it uses less digits than its factorization.

256840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6432 (or 6428 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 256840 is about 506.7938436879. The cubic root of 256840 is about 63.5654150533.

The spelling of 256840 in words is "two hundred fifty-six thousand, eight hundred forty".