28047821 has 4 divisors (see below), whose sum is σ = 28164444. Its totient is φ = 27931200.

The previous prime is 28047809. The next prime is 28047829. The reversal of 28047821 is 12874082.

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 25755625 + 2292196 = 5075^2 + 1514^2 .

It is a cyclic number.

It is not a de Polignac number, because 28047821 - 2⁶ = 28047757 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 (28047829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 57950 + ... + 58431.

It is an arithmetic number, because the mean of its divisors is an integer number (7041111).

Almost surely, 2^28047821 is an apocalyptic number.

It is an amenable number.

28047821 is a deficient number, since it is larger than the sum of its proper divisors (116623).

28047821 is a wasteful number, since it uses less digits than its factorization.

28047821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116622.

The product of its (nonzero) digits is 7168, while the sum is 32.

The square root of 28047821 is about 5296.0193541942. The cubic root of 28047821 is about 303.8316711522.

The spelling of 28047821 in words is "twenty-eight million, forty-seven thousand, eight hundred twenty-one".