81767185920 has 1440 divisors, whose sum is σ = 356292338688. Its totient is φ = 17235542016.

The previous prime is 81767185879. The next prime is 81767185979. The reversal of 81767185920 is 2958176718.

It is a tau number, because it is divible by the number of its divisors (1440).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 1220405727 + ... + 1220405793.

Almost surely, 2^81767185920 is an apocalyptic number.

81767185920 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81767185920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (178146169344).

81767185920 is an abundant number, since it is smaller than the sum of its proper divisors (274525152768).

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

81767185920 is a wasteful number, since it uses less digits than its factorization.

81767185920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180 (or 154 counting only the distinct ones).

The product of its (nonzero) digits is 1693440, while the sum is 54.

The spelling of 81767185920 in words is "eighty-one billion, seven hundred sixty-seven million, one hundred eighty-five thousand, nine hundred twenty".