28180805 has 4 divisors (see below), whose sum is σ = 33816972. Its totient is φ = 22544640.

The previous prime is 28180787. The next prime is 28180807. The reversal of 28180805 is 50808182.

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 13786369 + 14394436 = 3713^2 + 3794^2 .

It is not a de Polignac number, because 28180805 - 2⁸ = 28180549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28180807) 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, 2818076 + ... + 2818085.

It is an arithmetic number, because the mean of its divisors is an integer number (8454243).

Almost surely, 2^28180805 is an apocalyptic number.

It is an amenable number.

28180805 is a deficient number, since it is larger than the sum of its proper divisors (5636167).

28180805 is an equidigital number, since it uses as much as digits as its factorization.

28180805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5636166.

The product of its (nonzero) digits is 5120, while the sum is 32.

The square root of 28180805 is about 5308.5595974803. The cubic root of 28180805 is about 304.3111030625.

Adding to 28180805 its reverse (50808182), we get a palindrome (78988987).

The spelling of 28180805 in words is "twenty-eight million, one hundred eighty thousand, eight hundred five".