9989921 has 2 divisors, whose sum is σ = 9989922. Its totient is φ = 9989920.

The previous prime is 9989899. The next prime is 9989923. The reversal of 9989921 is 1299899.

9989921 is digitally balanced in base 3, 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., 9859600 + 130321 = 3140^2 + 361^2 .

It is an emirp because it is prime and its reverse (1299899) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9989921 is a prime.

Together with 9989923, 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 (9989923) 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, 4994960 + 4994961.

It is an arithmetic number, because the mean of its divisors is an integer number (4994961).

Almost surely, 2^9989921 is an apocalyptic number.

It is an amenable number.

9989921 is a deficient number, since it is larger than the sum of its proper divisors (1).

9989921 is an equidigital number, since it uses as much as digits as its factorization.

9989921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 104976, while the sum is 47.

The square root of 9989921 is about 3160.6836285842. The cubic root of 9989921 is about 215.3710628475.

The spelling of 9989921 in words is "nine million, nine hundred eighty-nine thousand, nine hundred twenty-one".