256438409 has 2 divisors, whose sum is σ = 256438410. Its totient is φ = 256438408.

The previous prime is 256438397. The next prime is 256438411. The reversal of 256438409 is 904834652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 254306809 + 2131600 = 15947^2 + 1460^2 .

It is a cyclic number.

It is not a de Polignac number, because 256438409 - 2⁴ = 256438393 is a prime.

It is a super-2 number, since 2×256438409² = 131521315220902562, which contains 22 as substring.

Together with 256438411, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (256438309) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128219204 + 128219205.

It is an arithmetic number, because the mean of its divisors is an integer number (128219205).

Almost surely, 2^256438409 is an apocalyptic number.

It is an amenable number.

256438409 is a deficient number, since it is larger than the sum of its proper divisors (1).

256438409 is an equidigital number, since it uses as much as digits as its factorization.

256438409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 207360, while the sum is 41.

The square root of 256438409 is about 16013.6944207138. The cubic root of 256438409 is about 635.3226780876.

The spelling of 256438409 in words is "two hundred fifty-six million, four hundred thirty-eight thousand, four hundred nine".