991787858754 has 432 divisors, whose sum is σ = 2665972304352. Its totient is φ = 245009318400.

The previous prime is 991787858749. The next prime is 991787858771. The reversal of 991787858754 is 457858787199.

It is a self number, because there is not a number n which added to its sum of digits gives 991787858754.

It is an unprimeable number.

It is a polite number, since it can be written in 215 ways as a sum of consecutive naturals, for example, 2290502922 + ... + 2290503354.

It is an arithmetic number, because the mean of its divisors is an integer number (6171232186).

Almost surely, 2^991787858754 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991787858754, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1332986152176).

991787858754 is an abundant number, since it is smaller than the sum of its proper divisors (1674184445598).

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

991787858754 is a wasteful number, since it uses less digits than its factorization.

991787858754 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 603 (or 554 counting only the distinct ones).

The product of its digits is 1422489600, while the sum is 78.

The spelling of 991787858754 in words is "nine hundred ninety-one billion, seven hundred eighty-seven million, eight hundred fifty-eight thousand, seven hundred fifty-four".