61721565728 has 48 divisors (see below), whose sum is σ = 126839877696. Its totient is φ = 29509159680.

The previous prime is 61721565709. The next prime is 61721565739. The reversal of 61721565728 is 82756512716.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2499683 + ... + 2524253.

It is an arithmetic number, because the mean of its divisors is an integer number (2642497452).

Almost surely, 2^61721565728 is an apocalyptic number.

It is an amenable number.

61721565728 is an abundant number, since it is smaller than the sum of its proper divisors (65118311968).

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

61721565728 is a wasteful number, since it uses less digits than its factorization.

61721565728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28017 (or 28009 counting only the distinct ones).

The product of its digits is 1411200, while the sum is 50.

The spelling of 61721565728 in words is "sixty-one billion, seven hundred twenty-one million, five hundred sixty-five thousand, seven hundred twenty-eight".