991986 has 8 divisors (see below), whose sum is σ = 1983984. Its totient is φ = 330660.

The previous prime is 991981. The next prime is 991987. The reversal of 991986 is 689199.

It is a sphenic number, since it is the product of 3 distinct primes.

991986 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (991981) by changing a digit.

991986 is an untouchable number, because it is not equal to the sum of proper divisors of any 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 3 ways as a sum of consecutive naturals, for example, 82660 + ... + 82671.

It is an arithmetic number, because the mean of its divisors is an integer number (247998).

2⁹⁹¹⁹⁸⁶ is an apocalyptic number.

991986 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

991986 is a wasteful number, since it uses less digits than its factorization.

991986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165336.

The product of its digits is 34992, while the sum is 42.

The square root of 991986 is about 995.9849396452. The cubic root of 991986 is about 99.7321498703.

The spelling of 991986 in words is "nine hundred ninety-one thousand, nine hundred eighty-six".