218906321 has 4 divisors (see below), whose sum is σ = 218990772. Its totient is φ = 218821872.

The previous prime is 218906293. The next prime is 218906333. The reversal of 218906321 is 123609812.

218906321 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.

It can be written as a sum of positive squares in 2 ways, for example, as 73342096 + 145564225 = 8564^2 + 12065^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218906321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (218906921) 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, 38210 + ... + 43563.

It is an arithmetic number, because the mean of its divisors is an integer number (54747693).

Almost surely, 2^218906321 is an apocalyptic number.

It is an amenable number.

218906321 is a deficient number, since it is larger than the sum of its proper divisors (84451).

218906321 is an equidigital number, since it uses as much as digits as its factorization.

218906321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84450.

The product of its (nonzero) digits is 5184, while the sum is 32.

The square root of 218906321 is about 14795.4831283064. The cubic root of 218906321 is about 602.6790579066.

The spelling of 218906321 in words is "two hundred eighteen million, nine hundred six thousand, three hundred twenty-one".