18135209 has 4 divisors (see below), whose sum is σ = 19202004. Its totient is φ = 17068416.

The previous prime is 18135203. The next prime is 18135223. The reversal of 18135209 is 90253181.

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

It can be written as a sum of positive squares in 2 ways, for example, as 15429184 + 2706025 = 3928^2 + 1645^2 .

It is a cyclic number.

It is not a de Polignac number, because 18135209 - 2⁴ = 18135193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18135203) 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, 533372 + ... + 533405.

It is an arithmetic number, because the mean of its divisors is an integer number (4800501).

Almost surely, 2^18135209 is an apocalyptic number.

It is an amenable number.

18135209 is a deficient number, since it is larger than the sum of its proper divisors (1066795).

18135209 is a wasteful number, since it uses less digits than its factorization.

18135209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1066794.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 18135209 is about 4258.5454089395. The cubic root of 18135209 is about 262.7287028770.

The spelling of 18135209 in words is "eighteen million, one hundred thirty-five thousand, two hundred nine".