991571 has 4 divisors (see below), whose sum is σ = 1133232. Its totient is φ = 849912.

The previous prime is 991567. The next prime is 991579. The reversal of 991571 is 175199.

991571 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 175199 = 19 ⋅9221.

It is not a de Polignac number, because 991571 - 2² = 991567 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991571.

It is not an unprimeable number, because it can be changed into a prime (991579) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70820 + ... + 70833.

It is an arithmetic number, because the mean of its divisors is an integer number (283308).

2⁹⁹¹⁵⁷¹ is an apocalyptic number.

991571 is a deficient number, since it is larger than the sum of its proper divisors (141661).

991571 is a wasteful number, since it uses less digits than its factorization.

991571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141660.

The product of its digits is 2835, while the sum is 32.

The square root of 991571 is about 995.7765813675. The cubic root of 991571 is about 99.7182401931.

The spelling of 991571 in words is "nine hundred ninety-one thousand, five hundred seventy-one".