9988721 has 2 divisors, whose sum is σ = 9988722. Its totient is φ = 9988720.

The previous prime is 9988711. The next prime is 9988733. The reversal of 9988721 is 1278899.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9388096 + 600625 = 3064^2 + 775^2 .

It is an emirp because it is prime and its reverse (1278899) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9988721 - 2²² = 5794417 is a prime.

It is a Chen prime.

It is a nialpdrome in base 10.

It is not a weakly prime, because it can be changed into another prime (9988711) 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, 4994360 + 4994361.

It is an arithmetic number, because the mean of its divisors is an integer number (4994361).

Almost surely, 2^9988721 is an apocalyptic number.

It is an amenable number.

9988721 is a deficient number, since it is larger than the sum of its proper divisors (1).

9988721 is an equidigital number, since it uses as much as digits as its factorization.

9988721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72576, while the sum is 44.

The square root of 9988721 is about 3160.4937905334. The cubic root of 9988721 is about 215.3624389681.

The spelling of 9988721 in words is "nine million, nine hundred eighty-eight thousand, seven hundred twenty-one".