18021609 has 28 divisors (see below), whose sum is σ = 27543600. Its totient is φ = 11782584.

The previous prime is 18021599. The next prime is 18021617. The reversal of 18021609 is 90612081.

It is not a de Polignac number, because 18021609 - 2¹² = 18017513 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (18021629) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 42802 + ... + 43220.

It is an arithmetic number, because the mean of its divisors is an integer number (983700).

Almost surely, 2^18021609 is an apocalyptic number.

It is an amenable number.

18021609 is a deficient number, since it is larger than the sum of its proper divisors (9521991).

18021609 is an frugal number, since it uses more digits than its factorization.

18021609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 496 (or 481 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 18021609 is about 4245.1865683383. The cubic root of 18021609 is about 262.1789708168.

The spelling of 18021609 in words is "eighteen million, twenty-one thousand, six hundred nine".