991191 has 8 divisors (see below), whose sum is σ = 1367280. Its totient is φ = 637952.

The previous prime is 991187. The next prime is 991201. The reversal of 991191 is 191199.

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 991191 - 2² = 991187 is a prime.

991191 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991191.

It is not an unprimeable number, because it can be changed into a prime (991171) 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, 5610 + ... + 5783.

It is an arithmetic number, because the mean of its divisors is an integer number (170910).

2⁹⁹¹¹⁹¹ is an apocalyptic number.

991191 is a deficient number, since it is larger than the sum of its proper divisors (376089).

991191 is a wasteful number, since it uses less digits than its factorization.

991191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11425.

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

The square root of 991191 is about 995.5857572304. The cubic root of 991191 is about 99.7055002168.

The spelling of 991191 in words is "nine hundred ninety-one thousand, one hundred ninety-one".