9918521 has 2 divisors, whose sum is σ = 9918522. Its totient is φ = 9918520.

The previous prime is 9918421. The next prime is 9918523. The reversal of 9918521 is 1258199.

9918521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9703225 + 215296 = 3115^2 + 464^2 .

It is a cyclic number.

It is not a de Polignac number, because 9918521 - 2¹⁸ = 9656377 is a prime.

It is a Sophie Germain prime.

Together with 9918523, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (9918523) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4959260 + 4959261.

It is an arithmetic number, because the mean of its divisors is an integer number (4959261).

Almost surely, 2^9918521 is an apocalyptic number.

It is an amenable number.

9918521 is a deficient number, since it is larger than the sum of its proper divisors (1).

9918521 is an equidigital number, since it uses as much as digits as its factorization.

9918521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6480, while the sum is 35.

The square root of 9918521 is about 3149.3683493679. The cubic root of 9918521 is about 214.8567352764.

The spelling of 9918521 in words is "nine million, nine hundred eighteen thousand, five hundred twenty-one".