1256662817 has 2 divisors, whose sum is σ = 1256662818. Its totient is φ = 1256662816.

The previous prime is 1256662811. The next prime is 1256662819. The reversal of 1256662817 is 7182666521.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 874030096 + 382632721 = 29564^2 + 19561^2 .

It is an emirp because it is prime and its reverse (7182666521) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1256662817 - 2⁴ = 1256662801 is a prime.

Together with 1256662819, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1256662811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 628331408 + 628331409.

It is an arithmetic number, because the mean of its divisors is an integer number (628331409).

Almost surely, 2^1256662817 is an apocalyptic number.

It is an amenable number.

1256662817 is a deficient number, since it is larger than the sum of its proper divisors (1).

1256662817 is an equidigital number, since it uses as much as digits as its factorization.

1256662817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 241920, while the sum is 44.

The square root of 1256662817 is about 35449.4402917733. The cubic root of 1256662817 is about 1079.1279016528.

The spelling of 1256662817 in words is "one billion, two hundred fifty-six million, six hundred sixty-two thousand, eight hundred seventeen".