28185905021 has 16 divisors (see below), whose sum is σ = 30092517360. Its totient is φ = 26307317760.

The previous prime is 28185904993. The next prime is 28185905057. The reversal of 28185905021 is 12050958182.

It can be written as a sum of positive squares in 8 ways, for example, as 167832025 + 28018072996 = 12955^2 + 167386^2 .

It is not a de Polignac number, because 28185905021 - 2¹⁰ = 28185903997 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 28185905021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28185905071) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2484041 + ... + 2495361.

It is an arithmetic number, because the mean of its divisors is an integer number (1880782335).

Almost surely, 2^28185905021 is an apocalyptic number.

It is an amenable number.

28185905021 is a deficient number, since it is larger than the sum of its proper divisors (1906612339).

28185905021 is a wasteful number, since it uses less digits than its factorization.

28185905021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12544.

The product of its (nonzero) digits is 57600, while the sum is 41.

The spelling of 28185905021 in words is "twenty-eight billion, one hundred eighty-five million, nine hundred five thousand, twenty-one".