18237521 has 4 divisors (see below), whose sum is σ = 18257844. Its totient is φ = 18217200.

The previous prime is 18237509. The next prime is 18237523. The reversal of 18237521 is 12573281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12573281 = 7 ⋅1796183.

It can be written as a sum of positive squares in 2 ways, for example, as 12780625 + 5456896 = 3575^2 + 2336^2 .

It is a cyclic number.

It is not a de Polignac number, because 18237521 - 2¹⁰ = 18236497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18237523) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8750 + ... + 10631.

It is an arithmetic number, because the mean of its divisors is an integer number (4564461).

Almost surely, 2^18237521 is an apocalyptic number.

It is an amenable number.

18237521 is a deficient number, since it is larger than the sum of its proper divisors (20323).

18237521 is an equidigital number, since it uses as much as digits as its factorization.

18237521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20322.

The product of its digits is 3360, while the sum is 29.

The square root of 18237521 is about 4270.5410664224. The cubic root of 18237521 is about 263.2218486942.

The spelling of 18237521 in words is "eighteen million, two hundred thirty-seven thousand, five hundred twenty-one".