821105820 has 72 divisors (see below), whose sum is σ = 2493835344. Its totient is φ = 218684928.

The previous prime is 821105783. The next prime is 821105827. The reversal of 821105820 is 28501128.

821105820 is a `hidden beast` number, since 82 + 1 + 1 + 0 + 582 + 0 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821105827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 168052 + ... + 172868.

It is an arithmetic number, because the mean of its divisors is an integer number (34636602).

Almost surely, 2^821105820 is an apocalyptic number.

It is an amenable number.

821105820 is an abundant number, since it is smaller than the sum of its proper divisors (1672729524).

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

821105820 is a wasteful number, since it uses less digits than its factorization.

821105820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5779 (or 5774 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 821105820 is about 28654.9440760229. The cubic root of 821105820 is about 936.4107199237.

Adding to 821105820 its reverse (28501128), we get a palindrome (849606948).

The spelling of 821105820 in words is "eight hundred twenty-one million, one hundred five thousand, eight hundred twenty".