9991831 has 4 divisors (see below), whose sum is σ = 10001664. Its totient is φ = 9982000.

The previous prime is 9991811. The next prime is 9991837. The reversal of 9991831 is 1381999.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 9991831 - 2¹³ = 9983639 is a prime.

It is a super-2 number, since 2×9991831² = 199673373465122, which contains 22 as substring.

It is a Duffinian number.

9991831 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9991837) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3190 + ... + 5491.

It is an arithmetic number, because the mean of its divisors is an integer number (2500416).

Almost surely, 2^9991831 is an apocalyptic number.

9991831 is a deficient number, since it is larger than the sum of its proper divisors (9833).

9991831 is a wasteful number, since it uses less digits than its factorization.

9991831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9832.

The product of its digits is 17496, while the sum is 40.

The square root of 9991831 is about 3160.9857639667. The cubic root of 9991831 is about 215.3847877648.

The spelling of 9991831 in words is "nine million, nine hundred ninety-one thousand, eight hundred thirty-one".