991043424 has 432 divisors, whose sum is σ = 3615993360. Its totient is φ = 266499072.

The previous prime is 991043413. The next prime is 991043429. The reversal of 991043424 is 424340199.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It is a tau number, because it is divible by the number of its divisors (432).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991043429) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 58296664 + ... + 58296680.

It is an arithmetic number, because the mean of its divisors is an integer number (8370355).

Almost surely, 2^991043424 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 991043424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1807996680).

991043424 is an abundant number, since it is smaller than the sum of its proper divisors (2624949936).

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

991043424 is an equidigital number, since it uses as much as digits as its factorization.

991043424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79 (or 29 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 991043424 is about 31480.8421742494. The cubic root of 991043424 is about 997.0055166868.

Multiplying 991043424 by its product of nonzero digits (31104), we get a square (30825414660096 = 5552064²).

The spelling of 991043424 in words is "nine hundred ninety-one million, forty-three thousand, four hundred twenty-four".