991861 has 6 divisors (see below), whose sum is σ = 1074210. Its totient is φ = 915408.

The previous prime is 991817. The next prime is 991867. The reversal of 991861 is 168199.

It can be written as a sum of positive squares in 3 ways, for example, as 52900 + 938961 = 230^2 + 969^2 .

It is not a de Polignac number, because 991861 - 2⁷ = 991733 is a prime.

It is a Duffinian 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 991861.

It is not an unprimeable number, because it can be changed into a prime (991867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2766 + ... + 3103.

It is an arithmetic number, because the mean of its divisors is an integer number (179035).

2⁹⁹¹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

991861 is a deficient number, since it is larger than the sum of its proper divisors (82349).

991861 is a wasteful number, since it uses less digits than its factorization.

991861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5895 (or 5882 counting only the distinct ones).

The product of its digits is 3888, while the sum is 34.

The square root of 991861 is about 995.9221857153. The cubic root of 991861 is about 99.7279606168.

The spelling of 991861 in words is "nine hundred ninety-one thousand, eight hundred sixty-one".