9991939121 has 8 divisors (see below), whose sum is σ = 10020972360. Its totient is φ = 9962929152.

The previous prime is 9991939117. The next prime is 9991939129. The reversal of 9991939121 is 1219391999.

It can be written as a sum of positive squares in 4 ways, for example, as 6550474225 + 3441464896 = 80935^2 + 58664^2 .

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 9991939121 - 2² = 9991939117 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9991939129) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1203641 + ... + 1211913.

It is an arithmetic number, because the mean of its divisors is an integer number (1252621545).

Almost surely, 2^9991939121 is an apocalyptic number.

It is an amenable number.

9991939121 is a deficient number, since it is larger than the sum of its proper divisors (29033239).

9991939121 is a wasteful number, since it uses less digits than its factorization.

9991939121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11635.

The product of its digits is 354294, while the sum is 53.

The square root of 9991939121 is about 99959.6874795035. The cubic root of 9991939121 is about 2153.8556465057.

The spelling of 9991939121 in words is "nine billion, nine hundred ninety-one million, nine hundred thirty-nine thousand, one hundred twenty-one".