821330221 has 4 divisors (see below), whose sum is σ = 825586012. Its totient is φ = 817074432.

The previous prime is 821330173. The next prime is 821330243. The reversal of 821330221 is 122033128.

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 321807721 + 499522500 = 17939^2 + 22350^2 .

It is a cyclic number.

It is not a de Polignac number, because 821330221 - 2⁷ = 821330093 is a prime.

It is a super-3 number, since 3×821330221³ (a number of 28 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 821330192 and 821330201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821330261) 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, 2127606 + ... + 2127991.

It is an arithmetic number, because the mean of its divisors is an integer number (206396503).

Almost surely, 2^821330221 is an apocalyptic number.

It is an amenable number.

821330221 is a deficient number, since it is larger than the sum of its proper divisors (4255791).

821330221 is a wasteful number, since it uses less digits than its factorization.

821330221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4255790.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 821330221 is about 28658.8593806523. The cubic root of 821330221 is about 936.4960164256.

Adding to 821330221 its reverse (122033128), we get a palindrome (943363349).

The spelling of 821330221 in words is "eight hundred twenty-one million, three hundred thirty thousand, two hundred twenty-one".