1256265691 has 2 divisors, whose sum is σ = 1256265692. Its totient is φ = 1256265690.

The previous prime is 1256265641. The next prime is 1256265697. The reversal of 1256265691 is 1965626521.

It is a strong prime.

It is an emirp because it is prime and its reverse (1965626521) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1256265691 is a prime.

It is not a weakly prime, because it can be changed into another prime (1256265697) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 628132845 + 628132846.

It is an arithmetic number, because the mean of its divisors is an integer number (628132846).

Almost surely, 2^1256265691 is an apocalyptic number.

1256265691 is a deficient number, since it is larger than the sum of its proper divisors (1).

1256265691 is an equidigital number, since it uses as much as digits as its factorization.

1256265691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 194400, while the sum is 43.

The square root of 1256265691 is about 35443.8385477645. The cubic root of 1256265691 is about 1079.0142156552.

The spelling of 1256265691 in words is "one billion, two hundred fifty-six million, two hundred sixty-five thousand, six hundred ninety-one".