81973907712 has 648 divisors, whose sum is σ = 266613669504. Its totient is φ = 25097859072.

The previous prime is 81973907699. The next prime is 81973907713. The reversal of 81973907712 is 21770937918.

It is a tau number, because it is divible by the number of its divisors (648).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81973907713) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1546677478 + ... + 1546677530.

It is an arithmetic number, because the mean of its divisors is an integer number (411440848).

Almost surely, 2^81973907712 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 81973907712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (133306834752).

81973907712 is an abundant number, since it is smaller than the sum of its proper divisors (184639761792).

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

81973907712 is an equidigital number, since it uses as much as digits as its factorization.

81973907712 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177 (or 128 counting only the distinct ones).

The product of its (nonzero) digits is 1333584, while the sum is 54.

The spelling of 81973907712 in words is "eighty-one billion, nine hundred seventy-three million, nine hundred seven thousand, seven hundred twelve".