18258521 has 4 divisors (see below), whose sum is σ = 18298932. Its totient is φ = 18218112.

The previous prime is 18258517. The next prime is 18258547. The reversal of 18258521 is 12585281.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12585281 = 1571 ⋅8011.

It can be written as a sum of positive squares in 2 ways, for example, as 14784025 + 3474496 = 3845^2 + 1864^2 .

It is a cyclic number.

It is not a de Polignac number, because 18258521 - 2² = 18258517 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18258421) 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, 19520 + ... + 20433.

It is an arithmetic number, because the mean of its divisors is an integer number (4574733).

Almost surely, 2^18258521 is an apocalyptic number.

It is an amenable number.

18258521 is a deficient number, since it is larger than the sum of its proper divisors (40411).

18258521 is an equidigital number, since it uses as much as digits as its factorization.

18258521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40410.

The product of its digits is 6400, while the sum is 32.

The square root of 18258521 is about 4272.9990638894. Note that the first 3 decimals coincide. The cubic root of 18258521 is about 263.3228408289.

The spelling of 18258521 in words is "eighteen million, two hundred fifty-eight thousand, five hundred twenty-one".