256718981 has 2 divisors, whose sum is σ = 256718982. Its totient is φ = 256718980.

The previous prime is 256718941. The next prime is 256718983. The reversal of 256718981 is 189817652.

256718981 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., 233050756 + 23668225 = 15266^2 + 4865^2 .

It is a cyclic number.

It is not a de Polignac number, because 256718981 - 2¹⁰ = 256717957 is a prime.

It is a super-2 number, since 2×256718981² = 131809270411356722, which contains 22 as substring.

Together with 256718983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256718983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128359490 + 128359491.

It is an arithmetic number, because the mean of its divisors is an integer number (128359491).

Almost surely, 2^256718981 is an apocalyptic number.

It is an amenable number.

256718981 is a deficient number, since it is larger than the sum of its proper divisors (1).

256718981 is an equidigital number, since it uses as much as digits as its factorization.

256718981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 241920, while the sum is 47.

The square root of 256718981 is about 16022.4524028003. The cubic root of 256718981 is about 635.5542980762.

The spelling of 256718981 in words is "two hundred fifty-six million, seven hundred eighteen thousand, nine hundred eighty-one".