9991920999 has 4 divisors (see below), whose sum is σ = 13322561336. Its totient is φ = 6661280664.

The previous prime is 9991920997. The next prime is 9991921033. The reversal of 9991920999 is 9990291999.

9991920999 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 9991920999 - 2¹ = 9991920997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9991920997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1665320164 + ... + 1665320169.

It is an arithmetic number, because the mean of its divisors is an integer number (3330640334).

Almost surely, 2^9991920999 is an apocalyptic number.

9991920999 is a deficient number, since it is larger than the sum of its proper divisors (3330640337).

9991920999 is a wasteful number, since it uses less digits than its factorization.

9991920999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3330640336.

The product of its (nonzero) digits is 9565938, while the sum is 66.

The square root of 9991920999 is about 99959.5968329204. The cubic root of 9991920999 is about 2153.8543443829.

The spelling of 9991920999 in words is "nine billion, nine hundred ninety-one million, nine hundred twenty thousand, nine hundred ninety-nine".