1256711917 has 2 divisors, whose sum is σ = 1256711918. Its totient is φ = 1256711916.

The previous prime is 1256711891. The next prime is 1256711941. The reversal of 1256711917 is 7191176521.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 652240521 + 604471396 = 25539^2 + 24586^2 .

It is an emirp because it is prime and its reverse (7191176521) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1256711917 - 2²³ = 1248323309 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1256711917.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1256711987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 628355958 + 628355959.

It is an arithmetic number, because the mean of its divisors is an integer number (628355959).

Almost surely, 2^1256711917 is an apocalyptic number.

It is an amenable number.

1256711917 is a deficient number, since it is larger than the sum of its proper divisors (1).

1256711917 is an equidigital number, since it uses as much as digits as its factorization.

1256711917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 26460, while the sum is 40.

The square root of 1256711917 is about 35450.1328206257. The cubic root of 1256711917 is about 1079.1419559372.

The spelling of 1256711917 in words is "one billion, two hundred fifty-six million, seven hundred eleven thousand, nine hundred seventeen".