218686813 has 4 divisors (see below), whose sum is σ = 218728188. Its totient is φ = 218645440.

The previous prime is 218686801. The next prime is 218686837. The reversal of 218686813 is 318686812.

218686813 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 3829849 + 214856964 = 1957^2 + 14658^2 .

It is a cyclic number.

It is not a de Polignac number, because 218686813 - 2⁵ = 218686781 is a prime.

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 218686813.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218686213) 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, 11356 + ... + 23797.

It is an arithmetic number, because the mean of its divisors is an integer number (54682047).

Almost surely, 2^218686813 is an apocalyptic number.

It is an amenable number.

218686813 is a deficient number, since it is larger than the sum of its proper divisors (41375).

218686813 is an equidigital number, since it uses as much as digits as its factorization.

218686813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41374.

The product of its digits is 110592, while the sum is 43.

The square root of 218686813 is about 14788.0631929945. The cubic root of 218686813 is about 602.4775453486.

Subtracting 218686813 from its reverse (318686812), we obtain a palindrome (99999999).

The spelling of 218686813 in words is "two hundred eighteen million, six hundred eighty-six thousand, eight hundred thirteen".