991908393600 has 192 divisors, whose sum is σ = 3268742796000. Its totient is φ = 264375767040.

The previous prime is 991908393569. The next prime is 991908393611. The reversal of 991908393600 is 6393809199.

It is a tau number, because it is divible by the number of its divisors (192).

It is a super-2 number, since 2×991908393600² (a number of 25 digits) contains 22 as substring.

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 23 ways as a sum of consecutive naturals, for example, 19837431 + ... + 19887369.

Almost surely, 2^991908393600 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 991908393600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1634371398000).

991908393600 is an abundant number, since it is smaller than the sum of its proper divisors (2276834402400).

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

991908393600 is a wasteful number, since it uses less digits than its factorization.

991908393600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52035 (or 52018 counting only the distinct ones).

The product of its (nonzero) digits is 2834352, while the sum is 57.

The spelling of 991908393600 in words is "nine hundred ninety-one billion, nine hundred eight million, three hundred ninety-three thousand, six hundred".