218109 has 16 divisors (see below), whose sum is σ = 316800. Its totient is φ = 133056.

The previous prime is 218107. The next prime is 218111. The reversal of 218109 is 901812.

It is an interprime number because it is at equal distance from previous prime (218107) and next prime (218111).

It is not a de Polignac number, because 218109 - 2¹ = 218107 is a prime.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218107) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1947 + ... + 2055.

It is an arithmetic number, because the mean of its divisors is an integer number (19800).

2²¹⁸¹⁰⁹ is an apocalyptic number.

218109 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

218109 is a deficient number, since it is larger than the sum of its proper divisors (98691).

218109 is a wasteful number, since it uses less digits than its factorization.

218109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 218109 is about 467.0214127853. The cubic root of 218109 is about 60.1946456462.

Adding to 218109 its sum of digits (21), we get a triangular number (218130 = T₆₆₀).

The spelling of 218109 in words is "two hundred eighteen thousand, one hundred nine".