821121 has 16 divisors (see below), whose sum is σ = 1273728. Its totient is φ = 460800.

The previous prime is 821113. The next prime is 821131. The reversal of 821121 is 121128.

821121 is a nontrivial binomial coefficient, being equal to C(1282, 2).

It is not a de Polignac number, because 821121 - 2³ = 821113 is a prime.

It is a Curzon number.

821121 is a lucky number.

It is a plaindrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 821121.

It is not an unprimeable number, because it can be changed into a prime (821101) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 961 + ... + 1601.

It is an arithmetic number, because the mean of its divisors is an integer number (79608).

2⁸²¹¹²¹ is an apocalyptic number.

821121 is the 1281-st triangular number and also the 641-st hexagonal number.

It is an amenable number.

821121 is a deficient number, since it is larger than the sum of its proper divisors (452607).

821121 is a wasteful number, since it uses less digits than its factorization.

821121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 712.

The product of its digits is 32, while the sum is 15.

The square root of 821121 is about 906.1572711180. The cubic root of 821121 is about 93.6416490446.

Adding to 821121 its reverse (121128), we get a palindrome (942249).

The spelling of 821121 in words is "eight hundred twenty-one thousand, one hundred twenty-one".