991840543 has 4 divisors (see below), whose sum is σ = 992606560. Its totient is φ = 991074528.

The previous prime is 991840529. The next prime is 991840579. The reversal of 991840543 is 345048199.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 345048199 = 37 ⋅9325627.

It is a cyclic number.

It is not a de Polignac number, because 991840543 - 2⁵ = 991840511 is a prime.

It is the 31494-th Hogben number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991840543.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991840643) by changing a digit.

It is a nontrivial repunit in base 31493.

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, 381063 + ... + 383656.

It is an arithmetic number, because the mean of its divisors is an integer number (248151640).

Almost surely, 2^991840543 is an apocalyptic number.

991840543 is a deficient number, since it is larger than the sum of its proper divisors (766017).

991840543 is a wasteful number, since it uses less digits than its factorization.

991840543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 766016.

The product of its (nonzero) digits is 155520, while the sum is 43.

The square root of 991840543 is about 31493.5000119072. The cubic root of 991840543 is about 997.2727498684.

The spelling of 991840543 in words is "nine hundred ninety-one million, eight hundred forty thousand, five hundred forty-three".