28561821 has 8 divisors (see below), whose sum is σ = 38251104. Its totient is φ = 18956880.

The previous prime is 28561787. The next prime is 28561823. The reversal of 28561821 is 12816582.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 28561821 - 2¹⁰ = 28560797 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28561823) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20290 + ... + 21651.

It is an arithmetic number, because the mean of its divisors is an integer number (4781388).

Almost surely, 2^28561821 is an apocalyptic number.

It is an amenable number.

28561821 is a deficient number, since it is larger than the sum of its proper divisors (9689283).

28561821 is a wasteful number, since it uses less digits than its factorization.

28561821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42171.

The product of its digits is 7680, while the sum is 33.

The square root of 28561821 is about 5344.3260566698. The cubic root of 28561821 is about 305.6764382875.

The spelling of 28561821 in words is "twenty-eight million, five hundred sixty-one thousand, eight hundred twenty-one".