256668691 has 2 divisors, whose sum is σ = 256668692. Its totient is φ = 256668690.

The previous prime is 256668683. The next prime is 256668697. The reversal of 256668691 is 196866652.

It is a happy number.

256668691 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 256668691 - 2³ = 256668683 is a prime.

It is not a weakly prime, because it can be changed into another prime (256668697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128334345 + 128334346.

It is an arithmetic number, because the mean of its divisors is an integer number (128334346).

Almost surely, 2^256668691 is an apocalyptic number.

256668691 is a deficient number, since it is larger than the sum of its proper divisors (1).

256668691 is an equidigital number, since it uses as much as digits as its factorization.

256668691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 933120, while the sum is 49.

The square root of 256668691 is about 16020.8829656795. The cubic root of 256668691 is about 635.5127947006.

The spelling of 256668691 in words is "two hundred fifty-six million, six hundred sixty-eight thousand, six hundred ninety-one".