256693891 has 2 divisors, whose sum is σ = 256693892. Its totient is φ = 256693890.

The previous prime is 256693883. The next prime is 256693909. The reversal of 256693891 is 198396652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256693891 - 2³ = 256693883 is a prime.

It is not a weakly prime, because it can be changed into another prime (256693841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128346945 + 128346946.

It is an arithmetic number, because the mean of its divisors is an integer number (128346946).

Almost surely, 2^256693891 is an apocalyptic number.

256693891 is a deficient number, since it is larger than the sum of its proper divisors (1).

256693891 is an equidigital number, since it uses as much as digits as its factorization.

256693891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 699840, while the sum is 49.

The square root of 256693891 is about 16021.6694198826. The cubic root of 256693891 is about 635.5335924564.

The spelling of 256693891 in words is "two hundred fifty-six million, six hundred ninety-three thousand, eight hundred ninety-one".