256440 has 32 divisors (see below), whose sum is σ = 769680. Its totient is φ = 68352.

The previous prime is 256423. The next prime is 256441. The reversal of 256440 is 44652.

It is a happy number.

It is a super-2 number, since 2×256440² = 131522947200, which contains 22 as substring.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 256440.

It is not an unprimeable number, because it can be changed into a prime (256441) by changing a digit.

256440 is an untouchable number, because it is not equal to the sum of proper divisors of any 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, 949 + ... + 1188.

2²⁵⁶⁴⁴⁰ is an apocalyptic number.

256440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

256440 is an abundant number, since it is smaller than the sum of its proper divisors (513240).

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

256440 is a wasteful number, since it uses less digits than its factorization.

256440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2151 (or 2147 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 256440 is about 506.3990521318. The cubic root of 256440 is about 63.5323991979.

It can be divided in two parts, 256 and 440, that added together give a palindrome (696).

The spelling of 256440 in words is "two hundred fifty-six thousand, four hundred forty".