256821823 has 2 divisors, whose sum is σ = 256821824. Its totient is φ = 256821822.

The previous prime is 256821797. The next prime is 256821853. The reversal of 256821823 is 328128652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256821823 - 2⁵ = 256821791 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256821853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128410911 + 128410912.

It is an arithmetic number, because the mean of its divisors is an integer number (128410912).

Almost surely, 2^256821823 is an apocalyptic number.

256821823 is a deficient number, since it is larger than the sum of its proper divisors (1).

256821823 is an equidigital number, since it uses as much as digits as its factorization.

256821823 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46080, while the sum is 37.

The square root of 256821823 is about 16025.6613904076. The cubic root of 256821823 is about 635.6391547404.

The spelling of 256821823 in words is "two hundred fifty-six million, eight hundred twenty-one thousand, eight hundred twenty-three".