28121811993 has 24 divisors (see below), whose sum is σ = 44320251456. Its totient is φ = 17040794400.

The previous prime is 28121811943. The next prime is 28121812027. The reversal of 28121811993 is 39911812182.

28121811993 is a `hidden beast` number, since 281 + 2 + 181 + 199 + 3 = 666.

It is not a de Polignac number, because 28121811993 - 2⁸ = 28121811737 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28121811923) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 721228 + ... + 759218.

It is an arithmetic number, because the mean of its divisors is an integer number (1846677144).

Almost surely, 2^28121811993 is an apocalyptic number.

It is an amenable number.

28121811993 is a deficient number, since it is larger than the sum of its proper divisors (16198439463).

28121811993 is a wasteful number, since it uses less digits than its factorization.

28121811993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45485 (or 45482 counting only the distinct ones).

The product of its digits is 62208, while the sum is 45.

The spelling of 28121811993 in words is "twenty-eight billion, one hundred twenty-one million, eight hundred eleven thousand, nine hundred ninety-three".