20688685 has 4 divisors (see below), whose sum is σ = 24826428. Its totient is φ = 16550944.

The previous prime is 20688671. The next prime is 20688691. The reversal of 20688685 is 58688602.

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 4959529 + 15729156 = 2227^2 + 3966^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20688685 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2068864 + ... + 2068873.

It is an arithmetic number, because the mean of its divisors is an integer number (6206607).

Almost surely, 2^20688685 is an apocalyptic number.

It is an amenable number.

20688685 is a deficient number, since it is larger than the sum of its proper divisors (4137743).

20688685 is an equidigital number, since it uses as much as digits as its factorization.

20688685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4137742.

The product of its (nonzero) digits is 184320, while the sum is 43.

The square root of 20688685 is about 4548.4816147809. The cubic root of 20688685 is about 274.5223001493.

The spelling of 20688685 in words is "twenty million, six hundred eighty-eight thousand, six hundred eighty-five".