256191 has 8 divisors (see below), whose sum is σ = 367920. Its totient is φ = 157632.

The previous prime is 256189. The next prime is 256199. The reversal of 256191 is 191652.

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

It is not a de Polignac number, because 256191 - 2¹ = 256189 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256199) 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, 3246 + ... + 3323.

It is an arithmetic number, because the mean of its divisors is an integer number (45990).

2²⁵⁶¹⁹¹ is an apocalyptic number.

256191 is a deficient number, since it is larger than the sum of its proper divisors (111729).

256191 is a wasteful number, since it uses less digits than its factorization.

256191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6585.

The product of its digits is 540, while the sum is 24.

The square root of 256191 is about 506.1531388819. The cubic root of 256191 is about 63.5118294865.

It can be divided in two parts, 25 and 6191, that added together give a triangular number (6216 = T₁₁₁).

The spelling of 256191 in words is "two hundred fifty-six thousand, one hundred ninety-one".