218506 has 4 divisors (see below), whose sum is σ = 327762. Its totient is φ = 109252.

The previous prime is 218479. The next prime is 218509. The reversal of 218506 is 605812.

It is a happy number.

218506 is digitally balanced in base 2 and base 3, because in such bases 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 only one way, i.e., 194481 + 24025 = 441^2 + 155^2 .

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (218509) by changing a digit.

218506 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 54625 + ... + 54628.

2²¹⁸⁵⁰⁶ is an apocalyptic number.

218506 is a deficient number, since it is larger than the sum of its proper divisors (109256).

218506 is a wasteful number, since it uses less digits than its factorization.

218506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109255.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 218506 is about 467.4462535950. The cubic root of 218506 is about 60.2311454234.

The spelling of 218506 in words is "two hundred eighteen thousand, five hundred six".