991591943 has 4 divisors (see below), whose sum is σ = 991698960. Its totient is φ = 991484928.

The previous prime is 991591933. The next prime is 991591949. The reversal of 991591943 is 349195199.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 349195199 = 113 ⋅3090223.

It is a cyclic number.

It is not a de Polignac number, because 991591943 - 2¹² = 991587847 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 991591891 and 991591900.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991591949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38138 + ... + 58631.

It is an arithmetic number, because the mean of its divisors is an integer number (247924740).

Almost surely, 2^991591943 is an apocalyptic number.

991591943 is a deficient number, since it is larger than the sum of its proper divisors (107017).

991591943 is a wasteful number, since it uses less digits than its factorization.

991591943 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107016.

The product of its digits is 393660, while the sum is 50.

The square root of 991591943 is about 31489.5529183887. The cubic root of 991591943 is about 997.1894223874.

The spelling of 991591943 in words is "nine hundred ninety-one million, five hundred ninety-one thousand, nine hundred forty-three".