256403 has 4 divisors (see below), whose sum is σ = 293040. Its totient is φ = 219768.

The previous prime is 256393. The next prime is 256423. The reversal of 256403 is 304652.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 256403 - 2⁸ = 256147 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 256403.

It is not an unprimeable number, because it can be changed into a prime (256423) 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, 18308 + ... + 18321.

It is an arithmetic number, because the mean of its divisors is an integer number (73260).

2²⁵⁶⁴⁰³ is an apocalyptic number.

256403 is a deficient number, since it is larger than the sum of its proper divisors (36637).

256403 is an equidigital number, since it uses as much as digits as its factorization.

256403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36636.

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 256403 is about 506.3625183601. The cubic root of 256403 is about 63.5293434969.

The spelling of 256403 in words is "two hundred fifty-six thousand, four hundred three".