81392312640 has 224 divisors, whose sum is σ = 264833648640. Its totient is φ = 21167548416.

The previous prime is 81392312593. The next prime is 81392312641. The reversal of 81392312640 is 4621329318.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81392312641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 39916741 + ... + 39918779.

Almost surely, 2^81392312640 is an apocalyptic number.

81392312640 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 81392312640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132416824320).

81392312640 is an abundant number, since it is smaller than the sum of its proper divisors (183441336000).

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

81392312640 is a wasteful number, since it uses less digits than its factorization.

81392312640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3069 (or 3059 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 39.

The spelling of 81392312640 in words is "eighty-one billion, three hundred ninety-two million, three hundred twelve thousand, six hundred forty".