991806 has 16 divisors (see below), whose sum is σ = 2070144. Its totient is φ = 316184.

The previous prime is 991777. The next prime is 991811. The reversal of 991806 is 608199.

It is a happy number.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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 991806.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 3456 + ... + 3731.

It is an arithmetic number, because the mean of its divisors is an integer number (129384).

2⁹⁹¹⁸⁰⁶ is an apocalyptic number.

991806 is an abundant number, since it is smaller than the sum of its proper divisors (1078338).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991806 is a wasteful number, since it uses less digits than its factorization.

991806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7215.

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 991806 is about 995.8945727335. The cubic root of 991806 is about 99.7261172338.

The spelling of 991806 in words is "nine hundred ninety-one thousand, eight hundred six".