28161505 has 4 divisors (see below), whose sum is σ = 33793812. Its totient is φ = 22529200.

The previous prime is 28161491. The next prime is 28161509. The reversal of 28161505 is 50516182.

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 17715681 + 10445824 = 4209^2 + 3232^2 .

It is not a de Polignac number, because 28161505 - 2⁵ = 28161473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28161509) 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, 2816146 + ... + 2816155.

It is an arithmetic number, because the mean of its divisors is an integer number (8448453).

Almost surely, 2^28161505 is an apocalyptic number.

It is an amenable number.

28161505 is a deficient number, since it is larger than the sum of its proper divisors (5632307).

28161505 is an equidigital number, since it uses as much as digits as its factorization.

28161505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5632306.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 28161505 is about 5306.7414672283. The cubic root of 28161505 is about 304.2416166919.

Adding to 28161505 its reverse (50516182), we get a palindrome (78677687).

The spelling of 28161505 in words is "twenty-eight million, one hundred sixty-one thousand, five hundred five".