991111778167680 has 384 divisors, whose sum is σ = 3800972326140000. Its totient is φ = 243965975445504.

The previous prime is 991111778167663. The next prime is 991111778167711. The reversal of 991111778167680 is 86761877111199.

It is a tau number, because it is divible by the number of its divisors (384).

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a junction number, because it is equal to n+sod(n) for n = 991111778167599 and 991111778167608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 166772005 + ... + 172612644.

Almost surely, 2^{991111778167680} is an apocalyptic number.

991111778167680 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

991111778167680 is an abundant number, since it is smaller than the sum of its proper divisors (2809860547972320).

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

991111778167680 is a wasteful number, since it uses less digits than its factorization.

991111778167680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 339384703 (or 339384672 counting only the distinct ones).

The product of its (nonzero) digits is 64012032, while the sum is 72.

The spelling of 991111778167680 in words is "nine hundred ninety-one trillion, one hundred eleven billion, seven hundred seventy-eight million, one hundred sixty-seven thousand, six hundred eighty".