991668 has 24 divisors (see below), whose sum is σ = 2415168. Its totient is φ = 316096.

The previous prime is 991663. The next prime is 991693. The reversal of 991668 is 866199.

991668 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 991668.

It is not an unprimeable number, because it can be changed into a prime (991663) by changing a digit.

991668 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1521 + ... + 2072.

It is an arithmetic number, because the mean of its divisors is an integer number (100632).

2⁹⁹¹⁶⁶⁸ is an apocalyptic number.

It is an amenable number.

991668 is an abundant number, since it is smaller than the sum of its proper divisors (1423500).

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

991668 is a wasteful number, since it uses less digits than its factorization.

991668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3623 (or 3621 counting only the distinct ones).

The product of its digits is 23328, while the sum is 39.

The square root of 991668 is about 995.8252858810. The cubic root of 991668 is about 99.7214917181.

The spelling of 991668 in words is "nine hundred ninety-one thousand, six hundred sixty-eight".