81730640 has 40 divisors (see below), whose sum is σ = 191726568. Its totient is φ = 32399360.

The previous prime is 81730567. The next prime is 81730657. The reversal of 81730640 is 4603718.

It can be written as a sum of positive squares in 4 ways, for example, as 9412624 + 72318016 = 3068^2 + 8504^2 .

It is a tau number, because it is divible by the number of its divisors (40).

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 7 ways as a sum of consecutive naturals, for example, 4520 + ... + 13560.

Almost surely, 2^81730640 is an apocalyptic number.

81730640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is a pronic number, being equal to 9040×9041.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81730640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95863284).

81730640 is an abundant number, since it is smaller than the sum of its proper divisors (109995928).

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

81730640 is a wasteful number, since it uses less digits than its factorization.

81730640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9167 (or 9161 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 81730640 is about 9040.4999861733. The cubic root of 81730640 is about 433.9719236865.

The spelling of 81730640 in words is "eighty-one million, seven hundred thirty thousand, six hundred forty".