991856128 has 40 divisors (see below), whose sum is σ = 1988466480. Its totient is φ = 494254080.

The previous prime is 991856123. The next prime is 991856147. The reversal of 991856128 is 821658199.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991856123) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 156118 + ... + 162346.

It is an arithmetic number, because the mean of its divisors is an integer number (49711662).

Almost surely, 2^991856128 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 991856128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (994233240).

991856128 is an abundant number, since it is smaller than the sum of its proper divisors (996610352).

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

991856128 is an equidigital number, since it uses as much as digits as its factorization.

991856128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6558 (or 6542 counting only the distinct ones).

The product of its digits is 311040, while the sum is 49.

The square root of 991856128 is about 31493.7474429449. The cubic root of 991856128 is about 997.2779732935.

The spelling of 991856128 in words is "nine hundred ninety-one million, eight hundred fifty-six thousand, one hundred twenty-eight".