685918109 has 4 divisors (see below), whose sum is σ = 686070300. Its totient is φ = 685765920.

The previous prime is 685918087. The next prime is 685918111. The reversal of 685918109 is 901819586.

685918109 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 an emirpimes, since its reverse is a distinct semiprime: 901819586 = 2 ⋅450909793.

It can be written as a sum of positive squares in 2 ways, for example, as 354568900 + 331349209 = 18830^2 + 18203^2 .

It is a cyclic number.

It is not a de Polignac number, because 685918109 - 2¹² = 685914013 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 (685918139) 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, 69122 + ... + 78419.

It is an arithmetic number, because the mean of its divisors is an integer number (171517575).

Almost surely, 2^685918109 is an apocalyptic number.

It is an amenable number.

685918109 is a deficient number, since it is larger than the sum of its proper divisors (152191).

685918109 is a wasteful number, since it uses less digits than its factorization.

685918109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152190.

The product of its (nonzero) digits is 155520, while the sum is 47.

The square root of 685918109 is about 26190.0383543056. The cubic root of 685918109 is about 881.9096395861.

The spelling of 685918109 in words is "six hundred eighty-five million, nine hundred eighteen thousand, one hundred nine".