218609 has 4 divisors (see below), whose sum is σ = 221760. Its totient is φ = 215460.

The previous prime is 218599. The next prime is 218611. The reversal of 218609 is 906812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 218609 - 2¹⁶ = 153073 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (218629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1469 + ... + 1610.

It is an arithmetic number, because the mean of its divisors is an integer number (55440).

2²¹⁸⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

218609 is a deficient number, since it is larger than the sum of its proper divisors (3151).

218609 is an equidigital number, since it uses as much as digits as its factorization.

218609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3150.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 218609 is about 467.5564137085. The cubic root of 218609 is about 60.2406079148.

The spelling of 218609 in words is "two hundred eighteen thousand, six hundred nine".