28388929 has 4 divisors (see below), whose sum is σ = 30058884. Its totient is φ = 26718976.

The previous prime is 28388909. The next prime is 28388947. The reversal of 28388929 is 92988382.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 92988382 = 2 ⋅46494191.

It can be written as a sum of positive squares in 2 ways, for example, as 15800625 + 12588304 = 3975^2 + 3548^2 .

It is a cyclic number.

It is not a de Polignac number, because 28388929 - 2¹⁵ = 28356161 is a prime.

It is a Smith number, since the sum of its digits (49) 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 (28388909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 834952 + ... + 834985.

It is an arithmetic number, because the mean of its divisors is an integer number (7514721).

Almost surely, 2^28388929 is an apocalyptic number.

It is an amenable number.

28388929 is a deficient number, since it is larger than the sum of its proper divisors (1669955).

28388929 is a wasteful number, since it uses less digits than its factorization.

28388929 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1669954.

The product of its digits is 497664, while the sum is 49.

The square root of 28388929 is about 5328.1262184749. The cubic root of 28388929 is about 305.0584103844.

The spelling of 28388929 in words is "twenty-eight million, three hundred eighty-eight thousand, nine hundred twenty-nine".