218321 has 4 divisors (see below), whose sum is σ = 219492. Its totient is φ = 217152.

The previous prime is 218287. The next prime is 218357. The reversal of 218321 is 123812.

218321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 25600 + 192721 = 160^2 + 439^2 .

It is a cyclic number.

It is not a de Polignac number, because 218321 - 2¹⁴ = 201937 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 218321.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 218321.

It is not an unprimeable number, because it can be changed into a prime (218371) 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, 236 + ... + 701.

It is an arithmetic number, because the mean of its divisors is an integer number (54873).

2²¹⁸³²¹ is an apocalyptic number.

It is an amenable number.

218321 is a deficient number, since it is larger than the sum of its proper divisors (1171).

218321 is an equidigital number, since it uses as much as digits as its factorization.

218321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1170.

The product of its digits is 96, while the sum is 17.

The square root of 218321 is about 467.2483279799. The cubic root of 218321 is about 60.2141422167.

The spelling of 218321 in words is "two hundred eighteen thousand, three hundred twenty-one".