991584 has 72 divisors (see below), whose sum is σ = 3085992. Its totient is φ = 299520.

The previous prime is 991579. The next prime is 991603. The reversal of 991584 is 485199.

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a congruent number.

It is an unprimeable number.

991584 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, 3012 + ... + 3324.

It is an arithmetic number, because the mean of its divisors is an integer number (42861).

2⁹⁹¹⁵⁸⁴ 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 991584, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1542996).

991584 is an abundant number, since it is smaller than the sum of its proper divisors (2094408).

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

991584 is a wasteful number, since it uses less digits than its factorization.

991584 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 340 (or 329 counting only the distinct ones).

The product of its digits is 12960, while the sum is 36.

The square root of 991584 is about 995.7831089148. The cubic root of 991584 is about 99.7186759768.

It can be divided in two parts, 9915 and 84, that added together give a palindrome (9999).

The spelling of 991584 in words is "nine hundred ninety-one thousand, five hundred eighty-four".