20121985 has 12 divisors (see below), whose sum is σ = 26147772. Its totient is φ = 14858688.

The previous prime is 20121973. The next prime is 20121989. The reversal of 20121985 is 58912102.

It can be written as a sum of positive squares in 6 ways, for example, as 3873024 + 16248961 = 1968^2 + 4031^2 .

It is not a de Polignac number, because 20121985 - 2¹⁵ = 20089217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20121989) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11062 + ... + 12751.

It is an arithmetic number, because the mean of its divisors is an integer number (2178981).

Almost surely, 2^20121985 is an apocalyptic number.

It is an amenable number.

20121985 is a deficient number, since it is larger than the sum of its proper divisors (6025787).

20121985 is a wasteful number, since it uses less digits than its factorization.

20121985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23844 (or 23831 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 20121985 is about 4485.7535598827. The cubic root of 20121985 is about 271.9925071826.

The spelling of 20121985 in words is "twenty million, one hundred twenty-one thousand, nine hundred eighty-five".