91993321728 has 576 divisors, whose sum is σ = 342089072640. Its totient is φ = 23688806400.

The previous prime is 91993321727. The next prime is 91993321799. The reversal of 91993321728 is 82712339919.

It is a tau number, because it is divible by the number of its divisors (576).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (91993321727) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 67591768 + ... + 67593128.

It is an arithmetic number, because the mean of its divisors is an integer number (593904640).

Almost surely, 2^91993321728 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 91993321728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (171044536320).

91993321728 is an abundant number, since it is smaller than the sum of its proper divisors (250095750912).

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

91993321728 is a wasteful number, since it uses less digits than its factorization.

91993321728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1531 (or 1511 counting only the distinct ones).

The product of its digits is 1469664, while the sum is 54.

The spelling of 91993321728 in words is "ninety-one billion, nine hundred ninety-three million, three hundred twenty-one thousand, seven hundred twenty-eight".