20400685 has 4 divisors (see below), whose sum is σ = 24480828. Its totient is φ = 16320544.

The previous prime is 20400683. The next prime is 20400689. The reversal of 20400685 is 58600402.

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 12482089 + 7918596 = 3533^2 + 2814^2 .

It is a cyclic number.

It is not a de Polignac number, because 20400685 - 2¹ = 20400683 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 (20400683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2040064 + ... + 2040073.

It is an arithmetic number, because the mean of its divisors is an integer number (6120207).

Almost surely, 2^20400685 is an apocalyptic number.

It is an amenable number.

20400685 is a deficient number, since it is larger than the sum of its proper divisors (4080143).

20400685 is an equidigital number, since it uses as much as digits as its factorization.

20400685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4080142.

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 20400685 is about 4516.7117463925. The cubic root of 20400685 is about 273.2424998925.

The spelling of 20400685 in words is "twenty million, four hundred thousand, six hundred eighty-five".