81978319488 has 128 divisors (see below), whose sum is σ = 234806040000. Its totient is φ = 25191751680.

The previous prime is 81978319483. The next prime is 81978319523. The reversal of 81978319488 is 88491387918.

It is a tau number, because it is divible by the number of its divisors (128).

It is not an unprimeable number, because it can be changed into a prime (81978319481) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4038388 + ... + 4058636.

Almost surely, 2^81978319488 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 81978319488, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117403020000).

81978319488 is an abundant number, since it is smaller than the sum of its proper divisors (152827720512).

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

81978319488 is a wasteful number, since it uses less digits than its factorization.

81978319488 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21090 (or 21078 counting only the distinct ones).

The product of its digits is 27869184, while the sum is 66.

The spelling of 81978319488 in words is "eighty-one billion, nine hundred seventy-eight million, three hundred nineteen thousand, four hundred eighty-eight".