18117521 has 2 divisors, whose sum is σ = 18117522. Its totient is φ = 18117520.

The previous prime is 18117509. The next prime is 18117523. The reversal of 18117521 is 12571181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13104400 + 5013121 = 3620^2 + 2239^2 .

It is a cyclic number.

It is not a de Polignac number, because 18117521 - 2¹⁴ = 18101137 is a prime.

Together with 18117523, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18117523) 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 as a sum of consecutive naturals, namely, 9058760 + 9058761.

It is an arithmetic number, because the mean of its divisors is an integer number (9058761).

Almost surely, 2^18117521 is an apocalyptic number.

It is an amenable number.

18117521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18117521 is an equidigital number, since it uses as much as digits as its factorization.

18117521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 560, while the sum is 26.

The square root of 18117521 is about 4256.4681368477. The cubic root of 18117521 is about 262.6432584621.

The spelling of 18117521 in words is "eighteen million, one hundred seventeen thousand, five hundred twenty-one".