91721440668 has 96 divisors (see below), whose sum is σ = 251583881472. Its totient is φ = 25640870400.

The previous prime is 91721440631. The next prime is 91721440673. The reversal of 91721440668 is 86604412719.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2992903 + ... + 3023393.

It is an arithmetic number, because the mean of its divisors is an integer number (2620665432).

Almost surely, 2^91721440668 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91721440668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (125791940736).

91721440668 is an abundant number, since it is smaller than the sum of its proper divisors (159862440804).

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

91721440668 is a wasteful number, since it uses less digits than its factorization.

91721440668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32275 (or 32273 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 48.

The spelling of 91721440668 in words is "ninety-one billion, seven hundred twenty-one million, four hundred forty thousand, six hundred sixty-eight".