18019521 has 24 divisors (see below), whose sum is σ = 28193256. Its totient is φ = 11024640.

The previous prime is 18019499. The next prime is 18019531. The reversal of 18019521 is 12591081.

It can be written as a sum of positive squares in 4 ways, for example, as 680625 + 17338896 = 825^2 + 4164^2 .

It is not a de Polignac number, because 18019521 - 2⁵ = 18019489 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18019531) 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 23 ways as a sum of consecutive naturals, for example, 26931 + ... + 27591.

It is an arithmetic number, because the mean of its divisors is an integer number (1174719).

Almost surely, 2^18019521 is an apocalyptic number.

It is an amenable number.

18019521 is a deficient number, since it is larger than the sum of its proper divisors (10173735).

18019521 is a wasteful number, since it uses less digits than its factorization.

18019521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 913 (or 910 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 27.

The square root of 18019521 is about 4244.9406356273. The cubic root of 18019521 is about 262.1688449945.

It can be divided in two parts, 180 and 19521, that added together give a triangular number (19701 = T₁₉₈).

The spelling of 18019521 in words is "eighteen million, nineteen thousand, five hundred twenty-one".