821663853631920 has 480 divisors, whose sum is σ = 3064818046858560. Its totient is φ = 202243169157120.

The previous prime is 821663853631919. The next prime is 821663853631939. The reversal of 821663853631920 is 29136358366128.

It is a happy number.

821663853631920 is a `hidden beast` number, since 8 + 2 + 1 + 6 + 6 + 3 + 8 + 536 + 3 + 1 + 92 + 0 = 666.

821663853631920 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 6787128190 + ... + 6787249250.

It is an arithmetic number, because the mean of its divisors is an integer number (6385037597622).

Almost surely, 2^{821663853631920} is an apocalyptic number.

821663853631920 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 821663853631920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1532409023429280).

821663853631920 is an abundant number, since it is smaller than the sum of its proper divisors (2243154193226640).

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

821663853631920 is a wasteful number, since it uses less digits than its factorization.

821663853631920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139702 (or 139677 counting only the distinct ones).

The product of its (nonzero) digits is 67184640, while the sum is 63.

The spelling of 821663853631920 in words is "eight hundred twenty-one trillion, six hundred sixty-three billion, eight hundred fifty-three million, six hundred thirty-one thousand, nine hundred twenty".