28638731657 has 4 divisors (see below), whose sum is σ = 28639192596. Its totient is φ = 28638270720.

The previous prime is 28638731599. The next prime is 28638731683. The reversal of 28638731657 is 75613783682.

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 23968922761 + 4669808896 = 154819^2 + 68336^2 .

It is a cyclic number.

It is not a de Polignac number, because 28638731657 - 2⁶ = 28638731593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28638731557) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 119444 + ... + 267477.

It is an arithmetic number, because the mean of its divisors is an integer number (7159798149).

Almost surely, 2^28638731657 is an apocalyptic number.

It is an amenable number.

28638731657 is a deficient number, since it is larger than the sum of its proper divisors (460939).

28638731657 is an equidigital number, since it uses as much as digits as its factorization.

28638731657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 460938.

The product of its digits is 10160640, while the sum is 56.

The spelling of 28638731657 in words is "twenty-eight billion, six hundred thirty-eight million, seven hundred thirty-one thousand, six hundred fifty-seven".