821371209 has 16 divisors (see below), whose sum is σ = 1102590720. Its totient is φ = 543876480.

The previous prime is 821371171. The next prime is 821371223. The reversal of 821371209 is 902173128.

It is not a de Polignac number, because 821371209 - 2¹⁷ = 821240137 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 821371209.

It is not an unprimeable number, because it can be changed into a prime (821371249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 666624 + ... + 667854.

It is an arithmetic number, because the mean of its divisors is an integer number (68911920).

Almost surely, 2^821371209 is an apocalyptic number.

It is an amenable number.

821371209 is a deficient number, since it is larger than the sum of its proper divisors (281219511).

821371209 is a wasteful number, since it uses less digits than its factorization.

821371209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2560.

The product of its (nonzero) digits is 6048, while the sum is 33.

The square root of 821371209 is about 28659.5744734635. The cubic root of 821371209 is about 936.5115945935.

The spelling of 821371209 in words is "eight hundred twenty-one million, three hundred seventy-one thousand, two hundred nine".