991619389440 has 864 divisors, whose sum is σ = 3771736375680. Its totient is φ = 240648192000.

The previous prime is 991619389399. The next prime is 991619389441. The reversal of 991619389440 is 44983916199.

991619389440 is a `hidden beast` number, since 9 + 9 + 1 + 619 + 3 + 8 + 9 + 4 + 4 + 0 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991619389441) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 825660840 + ... + 825662040.

It is an arithmetic number, because the mean of its divisors is an integer number (4365435620).

Almost surely, 2^991619389440 is an apocalyptic number.

991619389440 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 991619389440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1885868187840).

991619389440 is an abundant number, since it is smaller than the sum of its proper divisors (2780116986240).

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

991619389440 is a wasteful number, since it uses less digits than its factorization.

991619389440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1299 (or 1259 counting only the distinct ones).

The product of its (nonzero) digits is 15116544, while the sum is 63.

The spelling of 991619389440 in words is "nine hundred ninety-one billion, six hundred nineteen million, three hundred eighty-nine thousand, four hundred forty".