821121021 has 24 divisors (see below), whose sum is σ = 1359443904. Its totient is φ = 467847360.

The previous prime is 821121017. The next prime is 821121083. The reversal of 821121021 is 120121128.

It is not a de Polignac number, because 821121021 - 2² = 821121017 is a prime.

It is a super-2 number, since 2×821121021² = 1348479462256164882, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 821120985 and 821121003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821123021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3081 + ... + 40641.

It is an arithmetic number, because the mean of its divisors is an integer number (56643496).

Almost surely, 2^821121021 is an apocalyptic number.

It is an amenable number.

821121021 is a deficient number, since it is larger than the sum of its proper divisors (538322883).

821121021 is a wasteful number, since it uses less digits than its factorization.

821121021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37921 (or 37918 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

The square root of 821121021 is about 28655.2093169811. The cubic root of 821121021 is about 936.4164984284.

Adding to 821121021 its reverse (120121128), we get a palindrome (941242149).

The spelling of 821121021 in words is "eight hundred twenty-one million, one hundred twenty-one thousand, twenty-one".