81631722816 has 504 divisors, whose sum is σ = 298915531200. Its totient is φ = 20789747712.

The previous prime is 81631722793. The next prime is 81631722853. The reversal of 81631722816 is 61822713618.

81631722816 is a `hidden beast` number, since 8 + 1 + 631 + 7 + 2 + 2 + 8 + 1 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (504).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 24742735 + ... + 24746033.

Almost surely, 2^81631722816 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 81631722816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149457765600).

81631722816 is an abundant number, since it is smaller than the sum of its proper divisors (217283808384).

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

81631722816 is a wasteful number, since it uses less digits than its factorization.

81631722816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3379 (or 3347 counting only the distinct ones).

The product of its digits is 193536, while the sum is 45.

The spelling of 81631722816 in words is "eighty-one billion, six hundred thirty-one million, seven hundred twenty-two thousand, eight hundred sixteen".