218638081 has 4 divisors (see below), whose sum is σ = 218683732. Its totient is φ = 218592432.

The previous prime is 218638067. The next prime is 218638087. The reversal of 218638081 is 180836812.

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 110145025 + 108493056 = 10495^2 + 10416^2 .

It is a cyclic number.

It is not a de Polignac number, because 218638081 - 2¹³ = 218629889 is a prime.

It is a super-3 number, since 3×218638081³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

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 218638081.

It is not an unprimeable number, because it can be changed into a prime (218638087) 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, 14670 + ... + 25543.

It is an arithmetic number, because the mean of its divisors is an integer number (54670933).

Almost surely, 2^218638081 is an apocalyptic number.

It is an amenable number.

218638081 is a deficient number, since it is larger than the sum of its proper divisors (45651).

218638081 is an equidigital number, since it uses as much as digits as its factorization.

218638081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45650.

The product of its (nonzero) digits is 18432, while the sum is 37.

The square root of 218638081 is about 14786.4154209193. The cubic root of 218638081 is about 602.4327901476.

The spelling of 218638081 in words is "two hundred eighteen million, six hundred thirty-eight thousand, eighty-one".