218811 has 4 divisors (see below), whose sum is σ = 291752. Its totient is φ = 145872.

The previous prime is 218809. The next prime is 218819. The reversal of 218811 is 118812.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 218811 - 2¹ = 218809 is a prime.

It is a D-number.

It is a Duffinian number.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (218819) 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, 36466 + ... + 36471.

It is an arithmetic number, because the mean of its divisors is an integer number (72938).

2²¹⁸⁸¹¹ is an apocalyptic number.

218811 is a deficient number, since it is larger than the sum of its proper divisors (72941).

218811 is an equidigital number, since it uses as much as digits as its factorization.

218811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72940.

The product of its digits is 128, while the sum is 21.

The square root of 218811 is about 467.7723805442. The cubic root of 218811 is about 60.2591567954.

Subtracting from 218811 its reverse (118812), we obtain a palindrome (99999).

The spelling of 218811 in words is "two hundred eighteen thousand, eight hundred eleven".