256563491 has 2 divisors, whose sum is σ = 256563492. Its totient is φ = 256563490.

The previous prime is 256563487. The next prime is 256563509. The reversal of 256563491 is 194365652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256563491 - 2² = 256563487 is a prime.

It is not a weakly prime, because it can be changed into another prime (256563431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128281745 + 128281746.

It is an arithmetic number, because the mean of its divisors is an integer number (128281746).

Almost surely, 2^256563491 is an apocalyptic number.

256563491 is a deficient number, since it is larger than the sum of its proper divisors (1).

256563491 is an equidigital number, since it uses as much as digits as its factorization.

256563491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 194400, while the sum is 41.

The square root of 256563491 is about 16017.5994143942. The cubic root of 256563491 is about 635.4259576165.

The spelling of 256563491 in words is "two hundred fifty-six million, five hundred sixty-three thousand, four hundred ninety-one".