821810668 has 48 divisors (see below), whose sum is σ = 1780821504. Its totient is φ = 323769600.

The previous prime is 821810641. The next prime is 821810687. The reversal of 821810668 is 866018128.

It is a self number, because there is not a number n which added to its sum of digits gives 821810668.

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 15 ways as a sum of consecutive naturals, for example, 393 + ... + 40543.

It is an arithmetic number, because the mean of its divisors is an integer number (37100448).

Almost surely, 2^821810668 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 821810668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (890410752).

821810668 is an abundant number, since it is smaller than the sum of its proper divisors (959010836).

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

821810668 is a wasteful number, since it uses less digits than its factorization.

821810668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40222 (or 40220 counting only the distinct ones).

The product of its (nonzero) digits is 36864, while the sum is 40.

The square root of 821810668 is about 28667.2403275934. The cubic root of 821810668 is about 936.6785857044.

The spelling of 821810668 in words is "eight hundred twenty-one million, eight hundred ten thousand, six hundred sixty-eight".