27821 has 4 divisors (see below), whose sum is σ = 28512. Its totient is φ = 27132.

The previous prime is 27817. The next prime is 27823. The reversal of 27821 is 12872.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 27821 - 2² = 27817 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 27793 and 27802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27823) 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, 281 + ... + 366.

It is an arithmetic number, because the mean of its divisors is an integer number (7128).

2²⁷⁸²¹ is an apocalyptic number.

It is an amenable number.

27821 is a deficient number, since it is larger than the sum of its proper divisors (691).

27821 is an equidigital number, since it uses as much as digits as its factorization.

27821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 690.

The product of its digits is 224, while the sum is 20.

The square root of 27821 is about 166.7962829322. The cubic root of 27821 is about 30.3010430717.

It can be divided in two parts, 27 and 821, that added together give a palindrome (848).

The spelling of 27821 in words is "twenty-seven thousand, eight hundred twenty-one".