1991345328 has 240 divisors, whose sum is σ = 6615648000. Its totient is φ = 547305984.

The previous prime is 1991345297. The next prime is 1991345339. The reversal of 1991345328 is 8235431991.

It is a happy number.

1991345328 is a `hidden beast` number, since 199 + 1 + 3 + 453 + 2 + 8 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3990423 + ... + 3990921.

It is an arithmetic number, because the mean of its divisors is an integer number (27565200).

Almost surely, 2^1991345328 is an apocalyptic number.

1991345328 is a gapful number since it is divisible by the number (18) 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 1991345328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3307824000).

1991345328 is an abundant number, since it is smaller than the sum of its proper divisors (4624302672).

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

1991345328 is a wasteful number, since it uses less digits than its factorization.

1991345328 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 664 (or 655 counting only the distinct ones).

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

The square root of 1991345328 is about 44624.4924677021. The cubic root of 1991345328 is about 1258.1010548828.

The spelling of 1991345328 in words is "one billion, nine hundred ninety-one million, three hundred forty-five thousand, three hundred twenty-eight".