820557209 has 4 divisors (see below), whose sum is σ = 820984080. Its totient is φ = 820130340.

The previous prime is 820557193. The next prime is 820557217. The reversal of 820557209 is 902755028.

820557209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 820557209 - 2⁴ = 820557193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (820557239) 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, 210539 + ... + 214400.

It is an arithmetic number, because the mean of its divisors is an integer number (205246020).

Almost surely, 2^820557209 is an apocalyptic number.

It is an amenable number.

820557209 is a deficient number, since it is larger than the sum of its proper divisors (426871).

820557209 is a wasteful number, since it uses less digits than its factorization.

820557209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 426870.

The product of its (nonzero) digits is 50400, while the sum is 38.

The square root of 820557209 is about 28645.3697654612. The cubic root of 820557209 is about 936.2021233115.

The spelling of 820557209 in words is "eight hundred twenty million, five hundred fifty-seven thousand, two hundred nine".