256828321 has 16 divisors (see below), whose sum is σ = 270138960. Its totient is φ = 243855360.

The previous prime is 256828267. The next prime is 256828343. The reversal of 256828321 is 123828652.

It can be written as a sum of positive squares in 8 ways, for example, as 151560721 + 105267600 = 12311^2 + 10260^2 .

It is a 3-Lehmer number, since φ(256828321) divides (256828321-1)³.

It is a cyclic number.

It is a Carmichael number.

It is not a de Polignac number, because 256828321 - 2¹⁷ = 256697249 is a prime.

It is a deceptive number, since it divides R_256828320.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256828391) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 592921 + ... + 593353.

It is an arithmetic number, because the mean of its divisors is an integer number (16883685).

It is a Poulet number, since it divides 2^256828320-1.

Almost surely, 2^256828321 is an apocalyptic number.

It is an amenable number.

256828321 is a deficient number, since it is larger than the sum of its proper divisors (13310639).

256828321 is a wasteful number, since it uses less digits than its factorization.

256828321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 756.

The product of its digits is 46080, while the sum is 37.

The square root of 256828321 is about 16025.8641264676. The cubic root of 256828321 is about 635.6445155886.

The spelling of 256828321 in words is "two hundred fifty-six million, eight hundred twenty-eight thousand, three hundred twenty-one".