218905 has 4 divisors (see below), whose sum is σ = 262692. Its totient is φ = 175120.

The previous prime is 218887. The next prime is 218923. The reversal of 218905 is 509812.

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

It is an interprime number because it is at equal distance from previous prime (218887) and next prime (218923).

It can be written as a sum of positive squares in 2 ways, for example, as 166464 + 52441 = 408^2 + 229^2 .

It is not a de Polignac number, because 218905 - 2⁵ = 218873 is a prime.

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

It is a Duffinian number.

218905 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 218905.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21886 + ... + 21895.

It is an arithmetic number, because the mean of its divisors is an integer number (65673).

2²¹⁸⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

218905 is a deficient number, since it is larger than the sum of its proper divisors (43787).

218905 is an equidigital number, since it uses as much as digits as its factorization.

218905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43786.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 218905 is about 467.8728459742. The cubic root of 218905 is about 60.2677845606.

The spelling of 218905 in words is "two hundred eighteen thousand, nine hundred five".