28181605 has 16 divisors (see below), whose sum is σ = 34911360. Its totient is φ = 21822912.

The previous prime is 28181599. The next prime is 28181609. The reversal of 28181605 is 50618182.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28181605 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28181609) 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 15 ways as a sum of consecutive naturals, for example, 63976 + ... + 64414.

It is an arithmetic number, because the mean of its divisors is an integer number (2181960).

Almost surely, 2^28181605 is an apocalyptic number.

It is an amenable number.

28181605 is a deficient number, since it is larger than the sum of its proper divisors (6729755).

28181605 is a wasteful number, since it uses less digits than its factorization.

28181605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 828.

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 28181605 is about 5308.6349469520. The cubic root of 28181605 is about 304.3139826417.

Adding to 28181605 its reverse (50618182), we get a palindrome (78799787).

The spelling of 28181605 in words is "twenty-eight million, one hundred eighty-one thousand, six hundred five".