821686668 has 48 divisors (see below), whose sum is σ = 2097156096. Its totient is φ = 248330560.

The previous prime is 821686573. The next prime is 821686717. The reversal of 821686668 is 866686128.

It is a zygodrome in base 2.

It is a self number, because there is not a number n which added to its sum of digits gives 821686668.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42430 + ... + 58682.

It is an arithmetic number, because the mean of its divisors is an integer number (43690752).

Almost surely, 2^821686668 is an apocalyptic number.

It is an amenable number.

821686668 is an abundant number, since it is smaller than the sum of its proper divisors (1275469428).

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

821686668 is a wasteful number, since it uses less digits than its factorization.

821686668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16654 (or 16652 counting only the distinct ones).

The product of its digits is 1327104, while the sum is 51.

The square root of 821686668 is about 28665.0774985870. The cubic root of 821686668 is about 936.6314726683.

The spelling of 821686668 in words is "eight hundred twenty-one million, six hundred eighty-six thousand, six hundred sixty-eight".