99891991921 has 8 divisors (see below), whose sum is σ = 105161944320. Its totient is φ = 94623287472.

The previous prime is 99891991879. The next prime is 99891991933. The reversal of 99891991921 is 12919919899.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 99891991921 - 2¹³ = 99891983729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (99891991321) 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 7 ways as a sum of consecutive naturals, for example, 145390 + ... + 470023.

It is an arithmetic number, because the mean of its divisors is an integer number (13145243040).

Almost surely, 2^99891991921 is an apocalyptic number.

It is an amenable number.

99891991921 is a deficient number, since it is larger than the sum of its proper divisors (5269952399).

99891991921 is a wasteful number, since it uses less digits than its factorization.

99891991921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 623975.

The product of its digits is 8503056, while the sum is 67.

The spelling of 99891991921 in words is "ninety-nine billion, eight hundred ninety-one million, nine hundred ninety-one thousand, nine hundred twenty-one".