256557181 has 2 divisors, whose sum is σ = 256557182. Its totient is φ = 256557180.

The previous prime is 256557167. The next prime is 256557199. The reversal of 256557181 is 181755652.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 205205625 + 51351556 = 14325^2 + 7166^2 .

It is a cyclic number.

It is not a de Polignac number, because 256557181 - 2¹⁹ = 256032893 is a prime.

It is a super-2 number, since 2×256557181² = 131643174245333522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256557101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128278590 + 128278591.

It is an arithmetic number, because the mean of its divisors is an integer number (128278591).

Almost surely, 2^256557181 is an apocalyptic number.

It is an amenable number.

256557181 is a deficient number, since it is larger than the sum of its proper divisors (1).

256557181 is an equidigital number, since it uses as much as digits as its factorization.

256557181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 84000, while the sum is 40.

The square root of 256557181 is about 16017.4024423438. The cubic root of 256557181 is about 635.4207482878.

It can be divided in two parts, 2565571 and 81, that added together give a palindrome (2565652).

The spelling of 256557181 in words is "two hundred fifty-six million, five hundred fifty-seven thousand, one hundred eighty-one".