81718640640 has 1536 divisors, whose sum is σ = 376537896000. Its totient is φ = 16647192576.

The previous prime is 81718640623. The next prime is 81718640659. The reversal of 81718640640 is 4604681718.

It is a tau number, because it is divible by the number of its divisors (1536).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2817884146 + ... + 2817884174.

Almost surely, 2^81718640640 is an apocalyptic number.

81718640640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81718640640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (188268948000).

81718640640 is an abundant number, since it is smaller than the sum of its proper divisors (294819255360).

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

81718640640 is a wasteful number, since it uses less digits than its factorization.

81718640640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100 (or 59 counting only the distinct ones).

The product of its (nonzero) digits is 258048, while the sum is 45.

The spelling of 81718640640 in words is "eighty-one billion, seven hundred eighteen million, six hundred forty thousand, six hundred forty".