256191569 has 2 divisors, whose sum is σ = 256191570. Its totient is φ = 256191568.

The previous prime is 256191517. The next prime is 256191571. The reversal of 256191569 is 965191652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 232959169 + 23232400 = 15263^2 + 4820^2 .

It is a cyclic number.

It is not a de Polignac number, because 256191569 - 2¹² = 256187473 is a prime.

It is a super-2 number, since 2×256191569² = 131268240053363522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 256191571, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is equal to p_13999418 and since 256191569 and 13999418 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (256191869) 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 as a sum of consecutive naturals, namely, 128095784 + 128095785.

It is an arithmetic number, because the mean of its divisors is an integer number (128095785).

Almost surely, 2^256191569 is an apocalyptic number.

It is an amenable number.

256191569 is a deficient number, since it is larger than the sum of its proper divisors (1).

256191569 is an equidigital number, since it uses as much as digits as its factorization.

256191569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145800, while the sum is 44.

The square root of 256191569 is about 16005.9854117140. The cubic root of 256191569 is about 635.1187650634.

The spelling of 256191569 in words is "two hundred fifty-six million, one hundred ninety-one thousand, five hundred sixty-nine".