991791 has 16 divisors (see below), whose sum is σ = 1487200. Its totient is φ = 653184.

The previous prime is 991777. The next prime is 991811. The reversal of 991791 is 197199.

991791 is nontrivially palindromic in base 16.

It is not a de Polignac number, because 991791 - 2⁷ = 991663 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 (991741) by changing a digit.

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

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2775 + ... + 3111.

It is an arithmetic number, because the mean of its divisors is an integer number (92950).

2⁹⁹¹⁷⁹¹ is an apocalyptic number.

991791 is a deficient number, since it is larger than the sum of its proper divisors (495409).

991791 is a wasteful number, since it uses less digits than its factorization.

991791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 455 (or 449 counting only the distinct ones).

The product of its digits is 5103, while the sum is 36.

The square root of 991791 is about 995.8870417874. The cubic root of 991791 is about 99.7256144811.

The spelling of 991791 in words is "nine hundred ninety-one thousand, seven hundred ninety-one".