256491 has 6 divisors (see below), whose sum is σ = 370500. Its totient is φ = 170988.

The previous prime is 256489. The next prime is 256493. The reversal of 256491 is 194652.

It is an interprime number because it is at equal distance from previous prime (256489) and next prime (256493).

It is not a de Polignac number, because 256491 - 2¹ = 256489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (256493) 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 5 ways as a sum of consecutive naturals, for example, 14241 + ... + 14258.

It is an arithmetic number, because the mean of its divisors is an integer number (61750).

2²⁵⁶⁴⁹¹ is an apocalyptic number.

256491 is a deficient number, since it is larger than the sum of its proper divisors (114009).

256491 is a wasteful number, since it uses less digits than its factorization.

256491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28505 (or 28502 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 256491 is about 506.4494051729. The cubic root of 256491 is about 63.5366106282.

It can be divided in two parts, 256 and 491, that added together give a palindrome (747).

The spelling of 256491 in words is "two hundred fifty-six thousand, four hundred ninety-one".