28169905 has 4 divisors (see below), whose sum is σ = 33803892. Its totient is φ = 22535920.

The previous prime is 28169903. The next prime is 28169971. The reversal of 28169905 is 50996182.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50996182 = 2 ⋅25498091.

It can be written as a sum of positive squares in 2 ways, for example, as 16548624 + 11621281 = 4068^2 + 3409^2 .

It is not a de Polignac number, because 28169905 - 2¹ = 28169903 is a prime.

It is a Smith number, since the sum of its digits (40) 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 (28169903) 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, 2816986 + ... + 2816995.

It is an arithmetic number, because the mean of its divisors is an integer number (8450973).

Almost surely, 2^28169905 is an apocalyptic number.

It is an amenable number.

28169905 is a deficient number, since it is larger than the sum of its proper divisors (5633987).

28169905 is an equidigital number, since it uses as much as digits as its factorization.

28169905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5633986.

The product of its (nonzero) digits is 38880, while the sum is 40.

The square root of 28169905 is about 5307.5328543496. The cubic root of 28169905 is about 304.2718633652.

It can be divided in two parts, 2816 and 9905, that added together give a palindrome (12721).

The spelling of 28169905 in words is "twenty-eight million, one hundred sixty-nine thousand, nine hundred five".