81728720446 has 8 divisors (see below), whose sum is σ = 122609903040. Its totient is φ = 40858752768.

The previous prime is 81728720417. The next prime is 81728720461. The reversal of 81728720446 is 64402782718.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 81728720446.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2785486 + ... + 2814673.

It is an arithmetic number, because the mean of its divisors is an integer number (15326237880).

Almost surely, 2^81728720446 is an apocalyptic number.

81728720446 is a deficient number, since it is larger than the sum of its proper divisors (40881182594).

81728720446 is a wasteful number, since it uses less digits than its factorization.

81728720446 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5607458.

The product of its (nonzero) digits is 1204224, while the sum is 49.

The spelling of 81728720446 in words is "eighty-one billion, seven hundred twenty-eight million, seven hundred twenty thousand, four hundred forty-six".