28406565721 has 16 divisors (see below), whose sum is σ = 29757974400. Its totient is φ = 27081266688.

The previous prime is 28406565709. The next prime is 28406565727. The reversal of 28406565721 is 12756560482.

It is a cyclic number.

It is not a de Polignac number, because 28406565721 - 2⁵ = 28406565689 is a prime.

It is a super-2 number, since 2×28406565721² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28406565727) 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 15 ways as a sum of consecutive naturals, for example, 1223406 + ... + 1246408.

It is an arithmetic number, because the mean of its divisors is an integer number (1859873400).

Almost surely, 2^28406565721 is an apocalyptic number.

It is an amenable number.

28406565721 is a deficient number, since it is larger than the sum of its proper divisors (1351408679).

28406565721 is a wasteful number, since it uses less digits than its factorization.

28406565721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23568.

The product of its (nonzero) digits is 806400, while the sum is 46.

The spelling of 28406565721 in words is "twenty-eight billion, four hundred six million, five hundred sixty-five thousand, seven hundred twenty-one".