991911 has 8 divisors (see below), whose sum is σ = 1329664. Its totient is φ = 657720.

The previous prime is 991909. The next prime is 991927. The reversal of 991911 is 119199.

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

It is not a de Polignac number, because 991911 - 2¹ = 991909 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 (991901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is an upside-down number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 151 + ... + 1416.

It is an arithmetic number, because the mean of its divisors is an integer number (166208).

2⁹⁹¹⁹¹¹ is an apocalyptic number.

991911 is a deficient number, since it is larger than the sum of its proper divisors (337753).

991911 is a wasteful number, since it uses less digits than its factorization.

991911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1781.

The product of its digits is 729, while the sum is 30.

The square root of 991911 is about 995.9472877618. The cubic root of 991911 is about 99.7296363604.

The spelling of 991911 in words is "nine hundred ninety-one thousand, nine hundred eleven".