81981723744 has 36 divisors (see below), whose sum is σ = 233135527716. Its totient is φ = 27327241152.

The previous prime is 81981723737. The next prime is 81981723749. The reversal of 81981723744 is 44732718918.

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81981723749) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 142329094 + ... + 142329669.

It is an arithmetic number, because the mean of its divisors is an integer number (6475986881).

Almost surely, 2^81981723744 is an apocalyptic number.

It is an amenable number.

81981723744 is an abundant number, since it is smaller than the sum of its proper divisors (151153803972).

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

81981723744 is a wasteful number, since it uses less digits than its factorization.

81981723744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 284658779 (or 284658768 counting only the distinct ones).

The product of its digits is 2709504, while the sum is 54.

The spelling of 81981723744 in words is "eighty-one billion, nine hundred eighty-one million, seven hundred twenty-three thousand, seven hundred forty-four".