28638905 has 4 divisors (see below), whose sum is σ = 34366692. Its totient is φ = 22911120.

The previous prime is 28638893. The next prime is 28638923. The reversal of 28638905 is 50983682.

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 6661561 + 21977344 = 2581^2 + 4688^2 .

It is not a de Polignac number, because 28638905 - 2⁴ = 28638889 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2863886 + ... + 2863895.

It is an arithmetic number, because the mean of its divisors is an integer number (8591673).

Almost surely, 2^28638905 is an apocalyptic number.

It is an amenable number.

28638905 is a deficient number, since it is larger than the sum of its proper divisors (5727787).

28638905 is an equidigital number, since it uses as much as digits as its factorization.

28638905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5727786.

The product of its (nonzero) digits is 103680, while the sum is 41.

The square root of 28638905 is about 5351.5329579477. The cubic root of 28638905 is about 305.9511826377.

The spelling of 28638905 in words is "twenty-eight million, six hundred thirty-eight thousand, nine hundred five".