18189521 has 4 divisors (see below), whose sum is σ = 20788032. Its totient is φ = 15591012.

The previous prime is 18189487. The next prime is 18189539. The reversal of 18189521 is 12598181.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12598181 = 23 ⋅547747.

It is a cyclic number.

It is not a de Polignac number, because 18189521 - 2¹⁴ = 18173137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18189551) 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, 1299245 + ... + 1299258.

It is an arithmetic number, because the mean of its divisors is an integer number (5197008).

Almost surely, 2^18189521 is an apocalyptic number.

It is an amenable number.

18189521 is a deficient number, since it is larger than the sum of its proper divisors (2598511).

18189521 is an equidigital number, since it uses as much as digits as its factorization.

18189521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2598510.

The product of its digits is 5760, while the sum is 35.

The square root of 18189521 is about 4264.9174669623. The cubic root of 18189521 is about 262.9907180578.

The spelling of 18189521 in words is "eighteen million, one hundred eighty-nine thousand, five hundred twenty-one".