256617355821 has 8 divisors (see below), whose sum is σ = 342203677920. Its totient is φ = 171054635472.

The previous prime is 256617355783. The next prime is 256617355849. The reversal of 256617355821 is 128553716652.

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

It is not a de Polignac number, because 256617355821 - 2²⁶ = 256550246957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256617355861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5875051 + ... + 5918568.

It is an arithmetic number, because the mean of its divisors is an integer number (42775459740).

Almost surely, 2^256617355821 is an apocalyptic number.

It is an amenable number.

256617355821 is a deficient number, since it is larger than the sum of its proper divisors (85586322099).

256617355821 is a wasteful number, since it uses less digits than its factorization.

256617355821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11800875.

The product of its digits is 3024000, while the sum is 51.

The spelling of 256617355821 in words is "two hundred fifty-six billion, six hundred seventeen million, three hundred fifty-five thousand, eight hundred twenty-one".