28767639721 has 4 divisors (see below), whose sum is σ = 28770602112. Its totient is φ = 28764677332.

The previous prime is 28767639697. The next prime is 28767639863. The reversal of 28767639721 is 12793676782.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12793676782 = 2 ⋅6396838391.

It is a cyclic number.

It is not a de Polignac number, because 28767639721 - 2¹¹ = 28767637673 is a prime.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28767639521) 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, 1466581 + ... + 1486066.

It is an arithmetic number, because the mean of its divisors is an integer number (7192650528).

Almost surely, 2^28767639721 is an apocalyptic number.

It is an amenable number.

28767639721 is a deficient number, since it is larger than the sum of its proper divisors (2962391).

28767639721 is an equidigital number, since it uses as much as digits as its factorization.

28767639721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2962390.

The product of its digits is 10668672, while the sum is 58.

The spelling of 28767639721 in words is "twenty-eight billion, seven hundred sixty-seven million, six hundred thirty-nine thousand, seven hundred twenty-one".