81672944640 has 704 divisors, whose sum is σ = 310595862528. Its totient is φ = 17930649600.

The previous prime is 81672944629. The next prime is 81672944641. The reversal of 81672944640 is 4644927618.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81672944641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 427606945 + ... + 427607135.

Almost surely, 2^81672944640 is an apocalyptic number.

81672944640 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 81672944640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (155297931264).

81672944640 is an abundant number, since it is smaller than the sum of its proper divisors (228922917888).

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

81672944640 is a wasteful number, since it uses less digits than its factorization.

81672944640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 364 (or 346 counting only the distinct ones).

The product of its (nonzero) digits is 2322432, while the sum is 51.

The spelling of 81672944640 in words is "eighty-one billion, six hundred seventy-two million, nine hundred forty-four thousand, six hundred forty".