81681718712 has 128 divisors (see below), whose sum is σ = 176558745600. Its totient is φ = 35084275200.

The previous prime is 81681718691. The next prime is 81681718733. The reversal of 81681718712 is 21781718618.

It is an interprime number because it is at equal distance from previous prime (81681718691) and next prime (81681718733).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 33108503 + ... + 33110969.

It is an arithmetic number, because the mean of its divisors is an integer number (1379365200).

Almost surely, 2^81681718712 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 81681718712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (88279372800).

81681718712 is an abundant number, since it is smaller than the sum of its proper divisors (94877026888).

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

81681718712 is a wasteful number, since it uses less digits than its factorization.

81681718712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2797 (or 2793 counting only the distinct ones).

The product of its digits is 301056, while the sum is 50.

The spelling of 81681718712 in words is "eighty-one billion, six hundred eighty-one million, seven hundred eighteen thousand, seven hundred twelve".