81994508766 has 192 divisors, whose sum is σ = 210586521600. Its totient is φ = 23755286016.

The previous prime is 81994508663. The next prime is 81994508767. The reversal of 81994508766 is 66780549918.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81994508767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 5503315 + ... + 5518193.

It is an arithmetic number, because the mean of its divisors is an integer number (1096804800).

Almost surely, 2^81994508766 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81994508766, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105293260800).

81994508766 is an abundant number, since it is smaller than the sum of its proper divisors (128592012834).

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

81994508766 is a wasteful number, since it uses less digits than its factorization.

81994508766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14965 (or 14953 counting only the distinct ones).

The product of its (nonzero) digits is 26127360, while the sum is 63.

The spelling of 81994508766 in words is "eighty-one billion, nine hundred ninety-four million, five hundred eight thousand, seven hundred sixty-six".