28821 has 8 divisors (see below), whose sum is σ = 41440. Its totient is φ = 17712.

The previous prime is 28817. The next prime is 28837. The reversal of 28821 is 12882.

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

It is not a de Polignac number, because 28821 - 2² = 28817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 28821.

It is not an unprimeable number, because it can be changed into a prime (28871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 331 + ... + 408.

It is an arithmetic number, because the mean of its divisors is an integer number (5180).

2²⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

28821 is a deficient number, since it is larger than the sum of its proper divisors (12619).

28821 is a wasteful number, since it uses less digits than its factorization.

28821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 755.

The product of its digits is 256, while the sum is 21.

The square root of 28821 is about 169.7674880535. The cubic root of 28821 is about 30.6598257162.

The spelling of 28821 in words is "twenty-eight thousand, eight hundred twenty-one".