9988991 has 2 divisors, whose sum is σ = 9988992. Its totient is φ = 9988990.

The previous prime is 9988981. The next prime is 9989027. The reversal of 9988991 is 1998899.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9988991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9988921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4994495 + 4994496.

It is an arithmetic number, because the mean of its divisors is an integer number (4994496).

Almost surely, 2^9988991 is an apocalyptic number.

9988991 is a deficient number, since it is larger than the sum of its proper divisors (1).

9988991 is an equidigital number, since it uses as much as digits as its factorization.

9988991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 419904, while the sum is 53.

The square root of 9988991 is about 3160.5365050890. The cubic root of 9988991 is about 215.3643794012.

The spelling of 9988991 in words is "nine million, nine hundred eighty-eight thousand, nine hundred ninety-one".