10821 has 4 divisors (see below), whose sum is σ = 14432. Its totient is φ = 7212.

The previous prime is 10799. The next prime is 10831. The reversal of 10821 is 12801.

It is a happy number.

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 not a de Polignac number, because 10821 - 2⁵ = 10789 is a prime.

It is a D-number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 10797 and 10806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (10831) 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, 1801 + ... + 1806.

It is an arithmetic number, because the mean of its divisors is an integer number (3608).

2¹⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

10821 is a deficient number, since it is larger than the sum of its proper divisors (3611).

10821 is an equidigital number, since it uses as much as digits as its factorization.

10821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3610.

The product of its (nonzero) digits is 16, while the sum is 12.

The square root of 10821 is about 104.0240356841. The cubic root of 10821 is about 22.1185065051.

The spelling of 10821 in words is "ten thousand, eight hundred twenty-one".