991872 has 128 divisors (see below), whose sum is σ = 3427200. Its totient is φ = 276480.

The previous prime is 991871. The next prime is 991873. The reversal of 991872 is 278199.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (991871) and next prime (991873).

It is a tau number, because it is divible by the number of its divisors (128).

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

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (991871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24172 + ... + 24212.

It is an arithmetic number, because the mean of its divisors is an integer number (26775).

2⁹⁹¹⁸⁷² 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 991872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1713600).

991872 is an abundant number, since it is smaller than the sum of its proper divisors (2435328).

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

991872 is a wasteful number, since it uses less digits than its factorization.

991872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71 (or 53 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 991872 is about 995.9277082198. The cubic root of 991872 is about 99.7283292852.

The spelling of 991872 in words is "nine hundred ninety-one thousand, eight hundred seventy-two".