991635840 has 768 divisors, whose sum is σ = 4210315200. Its totient is φ = 212336640.

The previous prime is 991635839. The next prime is 991635851. The reversal of 991635840 is 48536199.

It is a happy number.

991635840 is a `hidden beast` number, since 9 + 9 + 1 + 63 + 584 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 24186220 + ... + 24186260.

Almost surely, 2^991635840 is an apocalyptic number.

991635840 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 991635840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2105157600).

991635840 is an abundant number, since it is smaller than the sum of its proper divisors (3218679360).

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

991635840 is a wasteful number, since it uses less digits than its factorization.

991635840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115 (or 100 counting only the distinct ones).

The product of its (nonzero) digits is 233280, while the sum is 45.

The square root of 991635840 is about 31490.2499196180. The cubic root of 991635840 is about 997.2041371023.

The spelling of 991635840 in words is "nine hundred ninety-one million, six hundred thirty-five thousand, eight hundred forty".