256328812721 has 2 divisors, whose sum is σ = 256328812722. Its totient is φ = 256328812720.

The previous prime is 256328812681. The next prime is 256328812759. The reversal of 256328812721 is 127218823652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 185210590321 + 71118222400 = 430361^2 + 266680^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256328812721 is a prime.

It is not a weakly prime, because it can be changed into another prime (256328812781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128164406360 + 128164406361.

It is an arithmetic number, because the mean of its divisors is an integer number (128164406361).

Almost surely, 2^256328812721 is an apocalyptic number.

It is an amenable number.

256328812721 is a deficient number, since it is larger than the sum of its proper divisors (1).

256328812721 is an equidigital number, since it uses as much as digits as its factorization.

256328812721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 645120, while the sum is 47.

The spelling of 256328812721 in words is "two hundred fifty-six billion, three hundred twenty-eight million, eight hundred twelve thousand, seven hundred twenty-one".