256778765 has 4 divisors (see below), whose sum is σ = 308134524. Its totient is φ = 205423008.

The previous prime is 256778759. The next prime is 256778783. The reversal of 256778765 is 567877652.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 67798756 + 188980009 = 8234^2 + 13747^2 .

It is a cyclic number.

It is not a de Polignac number, because 256778765 - 2¹⁶ = 256713229 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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 in 3 ways as a sum of consecutive naturals, for example, 25677872 + ... + 25677881.

It is an arithmetic number, because the mean of its divisors is an integer number (77033631).

Almost surely, 2^256778765 is an apocalyptic number.

It is an amenable number.

256778765 is a deficient number, since it is larger than the sum of its proper divisors (51355759).

256778765 is an equidigital number, since it uses as much as digits as its factorization.

256778765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51355758.

The product of its digits is 4939200, while the sum is 53.

The square root of 256778765 is about 16024.3179262020. The cubic root of 256778765 is about 635.6036296176.

The spelling of 256778765 in words is "two hundred fifty-six million, seven hundred seventy-eight thousand, seven hundred sixty-five".