816821258816 has 28 divisors (see below), whose sum is σ = 1676772092220. Its totient is φ = 394327503360.

The previous prime is 816821258809. The next prime is 816821258833. The reversal of 816821258816 is 618852128618.

It can be written as a sum of positive squares in 2 ways, for example, as 570169969216 + 246651289600 = 755096^2 + 496640^2 .

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 220046975 + ... + 220050686.

Almost surely, 2^816821258816 is an apocalyptic number.

It is an amenable number.

816821258816 is an abundant number, since it is smaller than the sum of its proper divisors (859950833404).

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

816821258816 is a wasteful number, since it uses less digits than its factorization.

816821258816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 440097702 (or 440097692 counting only the distinct ones).

The product of its digits is 2949120, while the sum is 56.

The spelling of 816821258816 in words is "eight hundred sixteen billion, eight hundred twenty-one million, two hundred fifty-eight thousand, eight hundred sixteen".