9009991 has 2 divisors, whose sum is σ = 9009992. Its totient is φ = 9009990.

The previous prime is 9009989. The next prime is 9010003. The reversal of 9009991 is 1999009.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 9009991 - 2¹ = 9009989 is a prime.

Together with 9009989, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 9009991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9009901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4504995 + 4504996.

It is an arithmetic number, because the mean of its divisors is an integer number (4504996).

Almost surely, 2^9009991 is an apocalyptic number.

9009991 is a deficient number, since it is larger than the sum of its proper divisors (1).

9009991 is an equidigital number, since it uses as much as digits as its factorization.

9009991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6561, while the sum is 37.

The square root of 9009991 is about 3001.6647047930. The cubic root of 9009991 is about 208.0853246462.

It can be divided in two parts, 9009 and 991, that added together give a 4-th power (10000 = 10⁴).

The spelling of 9009991 in words is "nine million, nine thousand, nine hundred ninety-one".