9991989 has 24 divisors (see below), whose sum is σ = 16598400. Its totient is φ = 5673888.

The previous prime is 9991973. The next prime is 9991997. The reversal of 9991989 is 9891999.

It is not a de Polignac number, because 9991989 - 2⁴ = 9991973 is a prime.

It is a super-2 number, since 2×9991989² = 199679688352242, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9991939) 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 in 23 ways as a sum of consecutive naturals, for example, 12139 + ... + 12935.

It is an arithmetic number, because the mean of its divisors is an integer number (691600).

Almost surely, 2^9991989 is an apocalyptic number.

It is an amenable number.

9991989 is a deficient number, since it is larger than the sum of its proper divisors (6606411).

9991989 is a wasteful number, since it uses less digits than its factorization.

9991989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1009 (or 1006 counting only the distinct ones).

The product of its digits is 472392, while the sum is 54.

The square root of 9991989 is about 3161.0107560715. The cubic root of 9991989 is about 215.3859230461.

The spelling of 9991989 in words is "nine million, nine hundred ninety-one thousand, nine hundred eighty-nine".