991791912672 has 144 divisors (see below), whose sum is σ = 3105565287552. Its totient is φ = 297734088960.

The previous prime is 991791912667. The next prime is 991791912697. The reversal of 991791912672 is 276219197199.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Smith number, since the sum of its digits (63) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1123948 + ... + 1801899.

It is an arithmetic number, because the mean of its divisors is an integer number (21566425608).

Almost surely, 2^991791912672 is an apocalyptic number.

It is an amenable number.

991791912672 is an abundant number, since it is smaller than the sum of its proper divisors (2113773374880).

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

991791912672 is a wasteful number, since it uses less digits than its factorization.

991791912672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2925981 (or 2925970 counting only the distinct ones).

The product of its digits is 7715736, while the sum is 63.

The spelling of 991791912672 in words is "nine hundred ninety-one billion, seven hundred ninety-one million, nine hundred twelve thousand, six hundred seventy-two".