991831 has 8 divisors (see below), whose sum is σ = 1076544. Its totient is φ = 910080.

The previous prime is 991817. The next prime is 991867. The reversal of 991831 is 138199.

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 991831 - 2⁷ = 991703 is a prime.

It is a super-2 number, since 2×991831² = 1967457465122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 991793 and 991802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991811) 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 7 ways as a sum of consecutive naturals, for example, 15 + ... + 1408.

It is an arithmetic number, because the mean of its divisors is an integer number (134568).

2⁹⁹¹⁸³¹ is an apocalyptic number.

991831 is a deficient number, since it is larger than the sum of its proper divisors (84713).

991831 is a wasteful number, since it uses less digits than its factorization.

991831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1481.

The product of its digits is 1944, while the sum is 31.

The square root of 991831 is about 995.9071241838. The cubic root of 991831 is about 99.7269551436.

The spelling of 991831 in words is "nine hundred ninety-one thousand, eight hundred thirty-one".