11111111109891 has 24 divisors (see below), whose sum is σ = 17610062900976. Its totient is φ = 6708595383360.

The previous prime is 11111111109881. The next prime is 11111111109911. The reversal of 11111111109891 is 19890111111111.

It is a happy number.

It is not a de Polignac number, because 11111111109891 - 2⁶ = 11111111109827 is a prime.

It is not an unprimeable number, because it can be changed into a prime (11111111109881) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 895906645 + ... + 895919046.

It is an arithmetic number, because the mean of its divisors is an integer number (733752620874).

Almost surely, 2^{11111111109891} is an apocalyptic number.

11111111109891 is a deficient number, since it is larger than the sum of its proper divisors (6498951791085).

11111111109891 is a wasteful number, since it uses less digits than its factorization.

11111111109891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1791825763 (or 1791825760 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 36.

The spelling of 11111111109891 in words is "eleven trillion, one hundred eleven billion, one hundred eleven million, one hundred nine thousand, eight hundred ninety-one".