256381 has 8 divisors (see below), whose sum is σ = 273024. Its totient is φ = 240240.

The previous prime is 256369. The next prime is 256391. The reversal of 256381 is 183652.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 256381 - 2⁵ = 256349 is a prime.

It is a super-2 number, since 2×256381² = 131462434322, which contains 22 as substring.

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

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256301) 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 7 ways as a sum of consecutive naturals, for example, 1555 + ... + 1711.

It is an arithmetic number, because the mean of its divisors is an integer number (34128).

2²⁵⁶³⁸¹ is an apocalyptic number.

It is an amenable number.

256381 is a deficient number, since it is larger than the sum of its proper divisors (16643).

256381 is a wasteful number, since it uses less digits than its factorization.

256381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 251.

The product of its digits is 1440, while the sum is 25.

The square root of 256381 is about 506.3407943273. The cubic root of 256381 is about 63.5275264543.

The spelling of 256381 in words is "two hundred fifty-six thousand, three hundred eighty-one".