8219921 has 4 divisors (see below), whose sum is σ = 8225844. Its totient is φ = 8214000.

The previous prime is 8219917. The next prime is 8219941. The reversal of 8219921 is 1299128.

It is a happy number.

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 4456321 + 3763600 = 2111^2 + 1940^2 .

It is a cyclic number.

It is not a de Polignac number, because 8219921 - 2² = 8219917 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8219941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 371 + ... + 4071.

It is an arithmetic number, because the mean of its divisors is an integer number (2056461).

Almost surely, 2^8219921 is an apocalyptic number.

It is an amenable number.

8219921 is a deficient number, since it is larger than the sum of its proper divisors (5923).

8219921 is a wasteful number, since it uses less digits than its factorization.

8219921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5922.

The product of its digits is 2592, while the sum is 32.

The square root of 8219921 is about 2867.0404601261. The cubic root of 8219921 is about 201.8161333792.

The spelling of 8219921 in words is "eight million, two hundred nineteen thousand, nine hundred twenty-one".