81211112100 has 108 divisors (see below), whose sum is σ = 254674689360. Its totient is φ = 21645835200.

The previous prime is 81211112069. The next prime is 81211112111. The reversal of 81211112100 is 121111218.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1940395 + ... + 1981805.

Almost surely, 2^81211112100 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81211112100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (127337344680).

81211112100 is an abundant number, since it is smaller than the sum of its proper divisors (173463577260).

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

81211112100 is a wasteful number, since it uses less digits than its factorization.

81211112100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43610 (or 43600 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 18.

Adding to 81211112100 its reverse (121111218), we get a palindrome (81332223318).

The spelling of 81211112100 in words is "eighty-one billion, two hundred eleven million, one hundred twelve thousand, one hundred".