821808 has 60 divisors (see below), whose sum is σ = 2482480. Its totient is φ = 252288.

The previous prime is 821803. The next prime is 821809. The reversal of 821808 is 808128.

It is a zygodrome in base 12.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 821808.

It is not an unprimeable number, because it can be changed into a prime (821801) by changing a digit.

821808 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1653 + ... + 2091.

2⁸²¹⁸⁰⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 821808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1241240).

821808 is an abundant number, since it is smaller than the sum of its proper divisors (1660672).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

821808 is a wasteful number, since it uses less digits than its factorization.

821808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 466 (or 457 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 27.

The square root of 821808 is about 906.5362651323. The cubic root of 821808 is about 93.6677572064.

The spelling of 821808 in words is "eight hundred twenty-one thousand, eight hundred eight".