991161 has 6 divisors (see below), whose sum is σ = 1431690. Its totient is φ = 660768.

The previous prime is 991147. The next prime is 991171. The reversal of 991161 is 161199.

It can be written as a sum of positive squares in only one way, i.e., 783225 + 207936 = 885^2 + 456^2 .

It is not a de Polignac number, because 991161 - 2⁵ = 991129 is a prime.

991161 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991161.

It is not an unprimeable number, because it can be changed into a prime (991171) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55056 + ... + 55073.

It is an arithmetic number, because the mean of its divisors is an integer number (238615).

2⁹⁹¹¹⁶¹ is an apocalyptic number.

It is an amenable number.

991161 is a deficient number, since it is larger than the sum of its proper divisors (440529).

991161 is a wasteful number, since it uses less digits than its factorization.

991161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110135 (or 110132 counting only the distinct ones).

The product of its digits is 486, while the sum is 27.

The square root of 991161 is about 995.5706906092. The cubic root of 991161 is about 99.7044942906.

The spelling of 991161 in words is "nine hundred ninety-one thousand, one hundred sixty-one".