81971801340 has 192 divisors, whose sum is σ = 270118582272. Its totient is φ = 18311270400.

The previous prime is 81971801297. The next prime is 81971801341. The reversal of 81971801340 is 4310817918.

It is a junction number, because it is equal to n+sod(n) for n = 81971801292 and 81971801301.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81971801341) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 5079885 + ... + 5095995.

It is an arithmetic number, because the mean of its divisors is an integer number (1406867616).

Almost surely, 2^81971801340 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 81971801340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (135059291136).

81971801340 is an abundant number, since it is smaller than the sum of its proper divisors (188146780932).

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

81971801340 is a wasteful number, since it uses less digits than its factorization.

81971801340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16740 (or 16738 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 42.

The spelling of 81971801340 in words is "eighty-one billion, nine hundred seventy-one million, eight hundred one thousand, three hundred forty".