18998521 has 4 divisors (see below), whose sum is σ = 19008000. Its totient is φ = 18989044.

The previous prime is 18998519. The next prime is 18998533. The reversal of 18998521 is 12589981.

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 a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12589981 = 1481 ⋅8501.

It is a cyclic number.

It is not a de Polignac number, because 18998521 - 2¹ = 18998519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18998321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 421 + ... + 6178.

It is an arithmetic number, because the mean of its divisors is an integer number (4752000).

Almost surely, 2^18998521 is an apocalyptic number.

It is an amenable number.

18998521 is a deficient number, since it is larger than the sum of its proper divisors (9479).

18998521 is an equidigital number, since it uses as much as digits as its factorization.

18998521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9478.

The product of its digits is 51840, while the sum is 43.

The square root of 18998521 is about 4358.7292873038. The cubic root of 18998521 is about 266.8332408925.

The spelling of 18998521 in words is "eighteen million, nine hundred ninety-eight thousand, five hundred twenty-one".