18409521 has 16 divisors (see below), whose sum is σ = 27990144. Its totient is φ = 10662144.

The previous prime is 18409513. The next prime is 18409529. The reversal of 18409521 is 12590481.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (18409513) and next prime (18409529).

It is not a de Polignac number, because 18409521 - 2³ = 18409513 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18409529) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13221 + ... + 14546.

It is an arithmetic number, because the mean of its divisors is an integer number (1749384).

Almost surely, 2^18409521 is an apocalyptic number.

It is an amenable number.

18409521 is a deficient number, since it is larger than the sum of its proper divisors (9580623).

18409521 is a wasteful number, since it uses less digits than its factorization.

18409521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27800.

The product of its (nonzero) digits is 2880, while the sum is 30.

The square root of 18409521 is about 4290.6317716625. The cubic root of 18409521 is about 264.0467519360.

The spelling of 18409521 in words is "eighteen million, four hundred nine thousand, five hundred twenty-one".