8321821 has 4 divisors (see below), whose sum is σ = 8327644. Its totient is φ = 8316000.

The previous prime is 8321813. The next prime is 8321843. The reversal of 8321821 is 1281238.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 509796 + 7812025 = 714^2 + 2795^2 .

It is a cyclic number.

It is not a de Polignac number, because 8321821 - 2³ = 8321813 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8321801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 871 + ... + 4171.

It is an arithmetic number, because the mean of its divisors is an integer number (2081911).

Almost surely, 2^8321821 is an apocalyptic number.

It is an amenable number.

8321821 is a deficient number, since it is larger than the sum of its proper divisors (5823).

8321821 is a wasteful number, since it uses less digits than its factorization.

8321821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5822.

The product of its digits is 768, while the sum is 25.

The square root of 8321821 is about 2884.7566621814. The cubic root of 8321821 is about 202.6466630452.

It can be divided in two parts, 83 and 21821, that added together give a square (21904 = 148²).

The spelling of 8321821 in words is "eight million, three hundred twenty-one thousand, eight hundred twenty-one".