256644673808543 has 2 divisors, whose sum is σ = 256644673808544. Its totient is φ = 256644673808542.

The previous prime is 256644673808539. The next prime is 256644673808561. The reversal of 256644673808543 is 345808376446652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256644673808543 - 2² = 256644673808539 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256644673801543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128322336904271 + 128322336904272.

It is an arithmetic number, because the mean of its divisors is an integer number (128322336904272).

Almost surely, 2^{256644673808543} is an apocalyptic number.

256644673808543 is a deficient number, since it is larger than the sum of its proper divisors (1).

256644673808543 is an equidigital number, since it uses as much as digits as its factorization.

256644673808543 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2786918400, while the sum is 71.

The spelling of 256644673808543 in words is "two hundred fifty-six trillion, six hundred forty-four billion, six hundred seventy-three million, eight hundred eight thousand, five hundred forty-three".