28113730721 has 4 divisors (see below), whose sum is σ = 28256440212. Its totient is φ = 27971021232.

The previous prime is 28113730717. The next prime is 28113730747. The reversal of 28113730721 is 12703731182.

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 26534781025 + 1578949696 = 162895^2 + 39736^2 .

It is a cyclic number.

It is not a de Polignac number, because 28113730721 - 2² = 28113730717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28113732721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71354450 + ... + 71354843.

It is an arithmetic number, because the mean of its divisors is an integer number (7064110053).

Almost surely, 2^28113730721 is an apocalyptic number.

It is an amenable number.

28113730721 is a deficient number, since it is larger than the sum of its proper divisors (142709491).

28113730721 is a wasteful number, since it uses less digits than its factorization.

28113730721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142709490.

The product of its (nonzero) digits is 14112, while the sum is 35.

The spelling of 28113730721 in words is "twenty-eight billion, one hundred thirteen million, seven hundred thirty thousand, seven hundred twenty-one".