820517909 has 4 divisors (see below), whose sum is σ = 848811660. Its totient is φ = 792224160.

The previous prime is 820517891. The next prime is 820517911. The reversal of 820517909 is 909715028.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 364695409 + 455822500 = 19097^2 + 21350^2 .

It is a cyclic number.

It is not a de Polignac number, because 820517909 - 2⁸ = 820517653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820517969) 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, 14146832 + ... + 14146889.

It is an arithmetic number, because the mean of its divisors is an integer number (212202915).

Almost surely, 2^820517909 is an apocalyptic number.

It is an amenable number.

820517909 is a deficient number, since it is larger than the sum of its proper divisors (28293751).

820517909 is a wasteful number, since it uses less digits than its factorization.

820517909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28293750.

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 820517909 is about 28644.6837825102. The cubic root of 820517909 is about 936.1871768294.

The spelling of 820517909 in words is "eight hundred twenty million, five hundred seventeen thousand, nine hundred nine".