820821 has 8 divisors (see below), whose sum is σ = 1098720. Its totient is φ = 545072.

The previous prime is 820793. The next prime is 820837. The reversal of 820821 is 128028.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 820821 - 2⁵ = 820789 is a prime.

It is a super-2 number, since 2×820821² = 1347494228082, which contains 22 as substring.

It is a nialpdrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820891) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 931 + ... + 1583.

It is an arithmetic number, because the mean of its divisors is an integer number (137340).

2⁸²⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

820821 is a deficient number, since it is larger than the sum of its proper divisors (277899).

820821 is a wasteful number, since it uses less digits than its factorization.

820821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1075.

The product of its (nonzero) digits is 256, while the sum is 21.

The square root of 820821 is about 905.9917218165. The cubic root of 820821 is about 93.6302435324.

Adding to 820821 its reverse (128028), we get a palindrome (948849).

The spelling of 820821 in words is "eight hundred twenty thousand, eight hundred twenty-one".