256166681 has 2 divisors, whose sum is σ = 256166682. Its totient is φ = 256166680.

The previous prime is 256166639. The next prime is 256166707. The reversal of 256166681 is 186661652.

It is a happy number.

256166681 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 can be written as a sum of positive squares in only one way, i.e., 221533456 + 34633225 = 14884^2 + 5885^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256166681 is a prime.

It is a super-2 number, since 2×256166681² = 131242736909111522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (216166681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128083340 + 128083341.

It is an arithmetic number, because the mean of its divisors is an integer number (128083341).

Almost surely, 2^256166681 is an apocalyptic number.

It is an amenable number.

256166681 is a deficient number, since it is larger than the sum of its proper divisors (1).

256166681 is an equidigital number, since it uses as much as digits as its factorization.

256166681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 41.

The square root of 256166681 is about 16005.2079336696. The cubic root of 256166681 is about 635.0981979701.

The spelling of 256166681 in words is "two hundred fifty-six million, one hundred sixty-six thousand, six hundred eighty-one".