91999999999891 has 8 divisors (see below), whose sum is σ = 92065462820864. Its totient is φ = 91934549371080.

The previous prime is 91999999999883. The next prime is 91999999999903. The reversal of 91999999999891 is 19899999999919.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 91999999999891 - 2³ = 91999999999883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91999999999091) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12075670 + ... + 18160996.

It is an arithmetic number, because the mean of its divisors is an integer number (11508182852608).

Almost surely, 2^{91999999999891} is an apocalyptic number.

91999999999891 is a deficient number, since it is larger than the sum of its proper divisors (65462820973).

91999999999891 is a wasteful number, since it uses less digits than its factorization.

91999999999891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6096081.

The product of its digits is 251048476872, while the sum is 109.

The spelling of 91999999999891 in words is "ninety-one trillion, nine hundred ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, eight hundred ninety-one".