81631994208 has 96 divisors (see below), whose sum is σ = 224710264800. Its totient is φ = 25912406016.

The previous prime is 81631994177. The next prime is 81631994239. The reversal of 81631994208 is 80249913618.

It is an interprime number because it is at equal distance from previous prime (81631994177) and next prime (81631994239).

It is a tau number, because it is divible by the number of its divisors (96).

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 15 ways as a sum of consecutive naturals, for example, 2398 + ... + 404066.

It is an arithmetic number, because the mean of its divisors is an integer number (2340731925).

Almost surely, 2^81631994208 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 81631994208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112355132400).

81631994208 is an abundant number, since it is smaller than the sum of its proper divisors (143078270592).

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

81631994208 is a wasteful number, since it uses less digits than its factorization.

81631994208 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 401784 (or 401776 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 51.

The spelling of 81631994208 in words is "eighty-one billion, six hundred thirty-one million, nine hundred ninety-four thousand, two hundred eight".