218273921 has 4 divisors (see below), whose sum is σ = 221852244. Its totient is φ = 214695600.

The previous prime is 218273911. The next prime is 218273947. The reversal of 218273921 is 129372812.

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 52765696 + 165508225 = 7264^2 + 12865^2 .

It is not a de Polignac number, because 218273921 - 2¹⁸ = 218011777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (218273911) 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, 1789070 + ... + 1789191.

It is an arithmetic number, because the mean of its divisors is an integer number (55463061).

Almost surely, 2^218273921 is an apocalyptic number.

It is an amenable number.

218273921 is a deficient number, since it is larger than the sum of its proper divisors (3578323).

218273921 is an equidigital number, since it uses as much as digits as its factorization.

218273921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3578322.

The product of its digits is 12096, while the sum is 35.

The square root of 218273921 is about 14774.0962836987. The cubic root of 218273921 is about 602.0981368912.

The spelling of 218273921 in words is "two hundred eighteen million, two hundred seventy-three thousand, nine hundred twenty-one".