28400665 has 4 divisors (see below), whose sum is σ = 34080804. Its totient is φ = 22720528.

The previous prime is 28400663. The next prime is 28400717. The reversal of 28400665 is 56600482.

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 22353984 + 6046681 = 4728^2 + 2459^2 .

It is a cyclic number.

It is not a de Polignac number, because 28400665 - 2¹ = 28400663 is a prime.

It is a Smith number, since the sum of its digits (31) 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 (28400663) 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, 2840062 + ... + 2840071.

It is an arithmetic number, because the mean of its divisors is an integer number (8520201).

Almost surely, 2^28400665 is an apocalyptic number.

It is an amenable number.

28400665 is a deficient number, since it is larger than the sum of its proper divisors (5680139).

28400665 is an equidigital number, since it uses as much as digits as its factorization.

28400665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5680138.

The product of its (nonzero) digits is 11520, while the sum is 31.

The square root of 28400665 is about 5329.2274299377. The cubic root of 28400665 is about 305.1004417020.

The spelling of 28400665 in words is "twenty-eight million, four hundred thousand, six hundred sixty-five".