18006209 has 4 divisors (see below), whose sum is σ = 19391316. Its totient is φ = 16621104.

The previous prime is 18006193. The next prime is 18006221. The reversal of 18006209 is 90260081.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90260081 = 197 ⋅458173.

It can be written as a sum of positive squares in 2 ways, for example, as 5382400 + 12623809 = 2320^2 + 3553^2 .

It is a cyclic number.

It is not a de Polignac number, because 18006209 - 2⁴ = 18006193 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 (18006259) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 692534 + ... + 692559.

It is an arithmetic number, because the mean of its divisors is an integer number (4847829).

Almost surely, 2^18006209 is an apocalyptic number.

It is an amenable number.

18006209 is a deficient number, since it is larger than the sum of its proper divisors (1385107).

18006209 is a wasteful number, since it uses less digits than its factorization.

18006209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1385106.

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

The square root of 18006209 is about 4243.3723616954. The cubic root of 18006209 is about 262.1042696295.

The spelling of 18006209 in words is "eighteen million, six thousand, two hundred nine".