20684689 has 4 divisors (see below), whose sum is σ = 20702500. Its totient is φ = 20666880.

The previous prime is 20684669. The next prime is 20684693. The reversal of 20684689 is 98648602.

It is a happy number.

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 3940225 + 16744464 = 1985^2 + 4092^2 .

It is a cyclic number.

It is not a de Polignac number, because 20684689 - 2⁷ = 20684561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20684639) 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, 7032 + ... + 9529.

It is an arithmetic number, because the mean of its divisors is an integer number (5175625).

Almost surely, 2^20684689 is an apocalyptic number.

It is an amenable number.

20684689 is a deficient number, since it is larger than the sum of its proper divisors (17811).

20684689 is a wasteful number, since it uses less digits than its factorization.

20684689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17810.

The product of its (nonzero) digits is 165888, while the sum is 43.

The square root of 20684689 is about 4548.0423261003. The cubic root of 20684689 is about 274.5046244367.

The spelling of 20684689 in words is "twenty million, six hundred eighty-four thousand, six hundred eighty-nine".