256817761 has 2 divisors, whose sum is σ = 256817762. Its totient is φ = 256817760.

The previous prime is 256817753. The next prime is 256817773. The reversal of 256817761 is 167718652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 236206161 + 20611600 = 15369^2 + 4540^2 .

It is a cyclic number.

It is not a de Polignac number, because 256817761 - 2³ = 256817753 is a prime.

It is not a weakly prime, because it can be changed into another prime (256817731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128408880 + 128408881.

It is an arithmetic number, because the mean of its divisors is an integer number (128408881).

Almost surely, 2^256817761 is an apocalyptic number.

It is an amenable number.

256817761 is a deficient number, since it is larger than the sum of its proper divisors (1).

256817761 is an equidigital number, since it uses as much as digits as its factorization.

256817761 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 43.

The square root of 256817761 is about 16025.5346556675. The cubic root of 256817761 is about 635.6358035456.

The spelling of 256817761 in words is "two hundred fifty-six million, eight hundred seventeen thousand, seven hundred sixty-one".