256817861 has 8 divisors (see below), whose sum is σ = 275368320. Its totient is φ = 238650048.

The previous prime is 256817849. The next prime is 256817909. The reversal of 256817861 is 168718652.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 256817861 - 2²⁶ = 189708997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256817161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 94271 + ... + 96956.

It is an arithmetic number, because the mean of its divisors is an integer number (34421040).

Almost surely, 2^256817861 is an apocalyptic number.

It is an amenable number.

256817861 is a deficient number, since it is larger than the sum of its proper divisors (18550459).

256817861 is a wasteful number, since it uses less digits than its factorization.

256817861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191323.

The product of its digits is 161280, while the sum is 44.

The square root of 256817861 is about 16025.5377756879. The cubic root of 256817861 is about 635.6358860472.

The spelling of 256817861 in words is "two hundred fifty-six million, eight hundred seventeen thousand, eight hundred sixty-one".