81102021891 has 16 divisors (see below), whose sum is σ = 117971365248. Its totient is φ = 49150745600.

The previous prime is 81102021887. The next prime is 81102021901. The reversal of 81102021891 is 19812020118.

It is not a de Polignac number, because 81102021891 - 2² = 81102021887 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (81102021811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1438096 + ... + 1493426.

It is an arithmetic number, because the mean of its divisors is an integer number (7373210328).

Almost surely, 2^81102021891 is an apocalyptic number.

81102021891 is a deficient number, since it is larger than the sum of its proper divisors (36869343357).

81102021891 is a wasteful number, since it uses less digits than its factorization.

81102021891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99762.

The product of its (nonzero) digits is 2304, while the sum is 33.

The spelling of 81102021891 in words is "eighty-one billion, one hundred two million, twenty-one thousand, eight hundred ninety-one".