685666209 has 4 divisors (see below), whose sum is σ = 914221616. Its totient is φ = 457110804.

The previous prime is 685666207. The next prime is 685666213. The reversal of 685666209 is 902666586.

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 not a de Polignac number, because 685666209 - 2¹ = 685666207 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (685666207) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 114277699 + ... + 114277704.

It is an arithmetic number, because the mean of its divisors is an integer number (228555404).

Almost surely, 2^685666209 is an apocalyptic number.

It is an amenable number.

685666209 is a deficient number, since it is larger than the sum of its proper divisors (228555407).

685666209 is a wasteful number, since it uses less digits than its factorization.

685666209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 228555406.

The product of its (nonzero) digits is 933120, while the sum is 48.

The square root of 685666209 is about 26185.2288323016. The cubic root of 685666209 is about 881.8016673973.

The spelling of 685666209 in words is "six hundred eighty-five million, six hundred sixty-six thousand, two hundred nine".