821230821 has 6 divisors (see below), whose sum is σ = 1186222310. Its totient is φ = 547487208.

The previous prime is 821230811. The next prime is 821230843. The reversal of 821230821 is 128032128.

It can be written as a sum of positive squares in only one way, i.e., 820822500 + 408321 = 28650^2 + 639^2 .

It is not a de Polignac number, because 821230821 - 2⁹ = 821230309 is a prime.

It is a super-2 number, since 2×821230821² = 1348840122720668082, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821230811) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 45623926 + ... + 45623943.

Almost surely, 2^821230821 is an apocalyptic number.

It is an amenable number.

821230821 is a deficient number, since it is larger than the sum of its proper divisors (364991489).

821230821 is a wasteful number, since it uses less digits than its factorization.

821230821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91247875 (or 91247872 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 821230821 is about 28657.1251349468. The cubic root of 821230821 is about 936.4582356576.

Adding to 821230821 its reverse (128032128), we get a palindrome (949262949).

The spelling of 821230821 in words is "eight hundred twenty-one million, two hundred thirty thousand, eight hundred twenty-one".