9991121 has 16 divisors (see below), whose sum is σ = 12213504. Its totient is φ = 7977984.

The previous prime is 9991067. The next prime is 9991123. The reversal of 9991121 is 1211999.

9991121 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 9991121 - 2⁶ = 9991057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9991123) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13076 + ... + 13818.

It is an arithmetic number, because the mean of its divisors is an integer number (763344).

Almost surely, 2^9991121 is an apocalyptic number.

It is an amenable number.

9991121 is a deficient number, since it is larger than the sum of its proper divisors (2222383).

9991121 is a wasteful number, since it uses less digits than its factorization.

9991121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 880.

The product of its digits is 1458, while the sum is 32.

The square root of 9991121 is about 3160.8734552335. The cubic root of 9991121 is about 215.3796860365.

The spelling of 9991121 in words is "nine million, nine hundred ninety-one thousand, one hundred twenty-one".