91721440664 has 32 divisors (see below), whose sum is σ = 200557092000. Its totient is φ = 39309187680.

The previous prime is 91721440631. The next prime is 91721440673. The reversal of 91721440664 is 46604412719.

It is a congruent number.

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, 16710347 + ... + 16715834.

It is an arithmetic number, because the mean of its divisors is an integer number (6267409125).

Almost surely, 2^91721440664 is an apocalyptic number.

It is an amenable number.

91721440664 is an abundant number, since it is smaller than the sum of its proper divisors (108835651336).

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

91721440664 is a wasteful number, since it uses less digits than its factorization.

91721440664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33426208 (or 33426190 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 44.

The spelling of 91721440664 in words is "ninety-one billion, seven hundred twenty-one million, four hundred forty thousand, six hundred sixty-four".