168821 has 4 divisors (see below), whose sum is σ = 169644. Its totient is φ = 168000.

The previous prime is 168803. The next prime is 168851. The reversal of 168821 is 128861.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 81796 + 87025 = 286^2 + 295^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-168821 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 (168851) 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, 191 + ... + 611.

It is an arithmetic number, because the mean of its divisors is an integer number (42411).

2¹⁶⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

168821 is a deficient number, since it is larger than the sum of its proper divisors (823).

168821 is an equidigital number, since it uses as much as digits as its factorization.

168821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 822.

The product of its digits is 768, while the sum is 26.

The square root of 168821 is about 410.8783274888. The cubic root of 168821 is about 55.2682215036.

It can be divided in two parts, 168 and 821, that added together give a palindrome (989).

The spelling of 168821 in words is "one hundred sixty-eight thousand, eight hundred twenty-one".