821866 has 8 divisors (see below), whose sum is σ = 1247904. Its totient is φ = 405900.

The previous prime is 821861. The next prime is 821869. The reversal of 821866 is 668128.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (821861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2310 + ... + 2641.

It is an arithmetic number, because the mean of its divisors is an integer number (155988).

2⁸²¹⁸⁶⁶ is an apocalyptic number.

821866 is a deficient number, since it is larger than the sum of its proper divisors (426038).

821866 is a wasteful number, since it uses less digits than its factorization.

821866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5036.

The product of its digits is 4608, while the sum is 31.

The square root of 821866 is about 906.5682544629. The cubic root of 821866 is about 93.6699607228.

The spelling of 821866 in words is "eight hundred twenty-one thousand, eight hundred sixty-six".