821311321 has 4 divisors (see below), whose sum is σ = 825480612. Its totient is φ = 817142032.

The previous prime is 821311297. The next prime is 821311331. The reversal of 821311321 is 123113128.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 407595721 + 413715600 = 20189^2 + 20340^2 .

It is a cyclic number.

It is not a de Polignac number, because 821311321 - 2⁵ = 821311289 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 821311292 and 821311301.

It is not an unprimeable number, because it can be changed into a prime (821311331) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2084350 + ... + 2084743.

It is an arithmetic number, because the mean of its divisors is an integer number (206370153).

Almost surely, 2^821311321 is an apocalyptic number.

It is an amenable number.

821311321 is a deficient number, since it is larger than the sum of its proper divisors (4169291).

821311321 is a wasteful number, since it uses less digits than its factorization.

821311321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4169290.

The product of its digits is 288, while the sum is 22.

The square root of 821311321 is about 28658.5296377885. The cubic root of 821311321 is about 936.4888329932.

Adding to 821311321 its reverse (123113128), we get a palindrome (944424449).

The spelling of 821311321 in words is "eight hundred twenty-one million, three hundred eleven thousand, three hundred twenty-one".