821221205 has 16 divisors (see below), whose sum is σ = 1126721664. Its totient is φ = 562885440.

The previous prime is 821221171. The next prime is 821221301. The reversal of 821221205 is 502122128.

It is a de Polignac number, because none of the positive numbers 2^k-821221205 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 134315 + ... + 140295.

It is an arithmetic number, because the mean of its divisors is an integer number (70420104).

Almost surely, 2^821221205 is an apocalyptic number.

It is an amenable number.

821221205 is a deficient number, since it is larger than the sum of its proper divisors (305500459).

821221205 is a wasteful number, since it uses less digits than its factorization.

821221205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9916.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 821221205 is about 28656.9573576819. The cubic root of 821221205 is about 936.4545805677.

The spelling of 821221205 in words is "eight hundred twenty-one million, two hundred twenty-one thousand, two hundred five".