991918764944640 has 1728 divisors, whose sum is σ = 4066541466624000. Its totient is φ = 220878619213824.

The previous prime is 991918764944629. The next prime is 991918764944711. The reversal of 991918764944640 is 46449467819199.

991918764944640 is a `hidden beast` number, since 9 + 9 + 1 + 9 + 1 + 8 + 7 + 64 + 94 + 464 + 0 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 991918764944640.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 39201614229 + ... + 39201639531.

It is an arithmetic number, because the mean of its divisors is an integer number (2353322608000).

Almost surely, 2^{991918764944640} is an apocalyptic number.

991918764944640 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 991918764944640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2033270733312000).

991918764944640 is an abundant number, since it is smaller than the sum of its proper divisors (3074622701679360).

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

991918764944640 is a wasteful number, since it uses less digits than its factorization.

991918764944640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25984 (or 25967 counting only the distinct ones).

The product of its (nonzero) digits is 3386105856, while the sum is 81.

The spelling of 991918764944640 in words is "nine hundred ninety-one trillion, nine hundred eighteen billion, seven hundred sixty-four million, nine hundred forty-four thousand, six hundred forty".