256405 has 8 divisors (see below), whose sum is σ = 324000. Its totient is φ = 194256.

The previous prime is 256393. The next prime is 256423. The reversal of 256405 is 504652.

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

It is not a de Polignac number, because 256405 - 2¹⁵ = 223637 is a prime.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 1255 + ... + 1444.

It is an arithmetic number, because the mean of its divisors is an integer number (40500).

2²⁵⁶⁴⁰⁵ is an apocalyptic number.

It is an amenable number.

256405 is a deficient number, since it is larger than the sum of its proper divisors (67595).

256405 is a wasteful number, since it uses less digits than its factorization.

256405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2723.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 256405 is about 506.3644932260. The cubic root of 256405 is about 63.5295086775.

The spelling of 256405 in words is "two hundred fifty-six thousand, four hundred five".