80821 has 4 divisors (see below), whose sum is σ = 87052. Its totient is φ = 74592.

The previous prime is 80819. The next prime is 80831. The reversal of 80821 is 12808.

It is a happy number.

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 34596 + 46225 = 186^2 + 215^2 .

It is a cyclic number.

It is not a de Polignac number, because 80821 - 2¹ = 80819 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 (80831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3096 + ... + 3121.

It is an arithmetic number, because the mean of its divisors is an integer number (21763).

2⁸⁰⁸²¹ is an apocalyptic number.

It is an amenable number.

80821 is a deficient number, since it is larger than the sum of its proper divisors (6231).

80821 is a wasteful number, since it uses less digits than its factorization.

80821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6230.

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 80821 is about 284.2903445423. The cubic root of 80821 is about 43.2355916677.

The spelling of 80821 in words is "eighty thousand, eight hundred twenty-one".