• 218 can be written using four 4's:

218 has 4 divisors (see below), whose sum is σ = 330. Its totient is φ = 108.

The previous prime is 211. The next prime is 223. The reversal of 218 is 812.

218 is nontrivially palindromic in base 9.

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

It can be written as a sum of positive squares in only one way, i.e., 169 + 49 = 13^2 + 7^2 .

It is an alternating number because its digits alternate between even and odd.

218 is an undulating number in base 9.

218 is a modest number, since divided by 18 gives 2 as remainder.

It is a plaindrome in base 5, base 11, base 13 and base 14.

It is a nialpdrome in base 7, base 8, base 15 and base 16.

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 199 and 208.

It is not an unprimeable number, because it can be changed into a prime (211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 53 + ... + 56.

2^{218} is an apocalyptic number.

218 is a deficient number, since it is larger than the sum of its proper divisors (112).

218 is a wasteful number, since it uses less digits than its factorization.

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

The sum of its prime factors is 111.

The product of its digits is 16, while the sum is 11.

The square root of 218 is about 14.7648230602. The cubic root of 218 is about 6.0184616548.

Subtracting from 218 its product of digits (16), we obtain a palindrome (202).

It can be divided in two parts, 2 and 18, that multiplied together give a triangular number (36 = T_{8}).

The spelling of 218 in words is "two hundred eighteen", and thus it is an aban number.

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