20905685 has 4 divisors (see below), whose sum is σ = 25086828. Its totient is φ = 16724544.

The previous prime is 20905679. The next prime is 20905711. The reversal of 20905685 is 58650902.

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 5982916 + 14922769 = 2446^2 + 3863^2 .

It is a cyclic number.

It is not a de Polignac number, because 20905685 - 2⁸ = 20905429 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, 2090564 + ... + 2090573.

It is an arithmetic number, because the mean of its divisors is an integer number (6271707).

Almost surely, 2^20905685 is an apocalyptic number.

It is an amenable number.

20905685 is a deficient number, since it is larger than the sum of its proper divisors (4181143).

20905685 is an equidigital number, since it uses as much as digits as its factorization.

20905685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4181142.

The product of its (nonzero) digits is 21600, while the sum is 35.

The square root of 20905685 is about 4572.2735045052. The cubic root of 20905685 is about 275.4787692947.

The spelling of 20905685 in words is "twenty million, nine hundred five thousand, six hundred eighty-five".