256565917 has 2 divisors, whose sum is σ = 256565918. Its totient is φ = 256565916.

The previous prime is 256565899. The next prime is 256565963. The reversal of 256565917 is 719565652.

It is an a-pointer prime, because the next prime (256565963) can be obtained adding 256565917 to its sum of digits (46).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 195272676 + 61293241 = 13974^2 + 7829^2 .

It is a cyclic number.

It is not a de Polignac number, because 256565917 - 2²³ = 248177309 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256565317) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128282958 + 128282959.

It is an arithmetic number, because the mean of its divisors is an integer number (128282959).

Almost surely, 2^256565917 is an apocalyptic number.

It is an amenable number.

256565917 is a deficient number, since it is larger than the sum of its proper divisors (1).

256565917 is an equidigital number, since it uses as much as digits as its factorization.

256565917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 567000, while the sum is 46.

The square root of 256565917 is about 16017.6751434158. The cubic root of 256565917 is about 635.4279604196.

The spelling of 256565917 in words is "two hundred fifty-six million, five hundred sixty-five thousand, nine hundred seventeen".