18307521 has 12 divisors (see below), whose sum is σ = 27999972. Its totient is φ = 11486976.

The previous prime is 18307511. The next prime is 18307547. The reversal of 18307521 is 12570381.

It can be written as a sum of positive squares in 2 ways, for example, as 9090225 + 9217296 = 3015^2 + 3036^2 .

It is a de Polignac number, because none of the positive numbers 2^k-18307521 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18307501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59676 + ... + 59981.

It is an arithmetic number, because the mean of its divisors is an integer number (2333331).

Almost surely, 2^18307521 is an apocalyptic number.

It is an amenable number.

18307521 is a deficient number, since it is larger than the sum of its proper divisors (9692451).

18307521 is a wasteful number, since it uses less digits than its factorization.

18307521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119680 (or 119677 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 18307521 is about 4278.7289000356. The cubic root of 18307521 is about 263.5581883695.

The spelling of 18307521 in words is "eighteen million, three hundred seven thousand, five hundred twenty-one".