991908 has 36 divisors (see below), whose sum is σ = 2555280. Its totient is φ = 324336.

The previous prime is 991901. The next prime is 991909. The reversal of 991908 is 809199.

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991908.

It is not an unprimeable number, because it can be changed into a prime (991901) by changing a digit.

991908 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 11 ways as a sum of consecutive naturals, for example, 1891 + ... + 2357.

It is an arithmetic number, because the mean of its divisors is an integer number (70980).

2⁹⁹¹⁹⁰⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991908, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1277640).

991908 is an abundant number, since it is smaller than the sum of its proper divisors (1563372).

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

991908 is a wasteful number, since it uses less digits than its factorization.

991908 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 536 (or 531 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 36.

The square root of 991908 is about 995.9457816568. The cubic root of 991908 is about 99.7295358174.

The spelling of 991908 in words is "nine hundred ninety-one thousand, nine hundred eight".