999638640 has 960 divisors, whose sum is σ = 4809692160. Its totient is φ = 179159040.

The previous prime is 999638623. The next prime is 999638663. The reversal of 999638640 is 46836999.

It is a happy number.

999638640 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 unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 13693644 + ... + 13693716.

It is an arithmetic number, because the mean of its divisors is an integer number (5010096).

Almost surely, 2^999638640 is an apocalyptic number.

999638640 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 999638640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2404846080).

999638640 is an abundant number, since it is smaller than the sum of its proper divisors (3810053520).

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

999638640 is a wasteful number, since it uses less digits than its factorization.

999638640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142 (or 133 counting only the distinct ones).

The product of its (nonzero) digits is 2519424, while the sum is 54.

The square root of 999638640 is about 31617.0624821472. The cubic root of 999638640 is about 999.8795321547.

The spelling of 999638640 in words is "nine hundred ninety-nine million, six hundred thirty-eight thousand, six hundred forty".