9999721872 has 240 divisors, whose sum is σ = 32458458240. Its totient is φ = 2815008768.

The previous prime is 9999721867. The next prime is 9999721873. The reversal of 9999721872 is 2781279999.

It is a Harshad number since it is a multiple of its sum of digits (63).

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 (9999721873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 28327648 + ... + 28328000.

It is an arithmetic number, because the mean of its divisors is an integer number (135243576).

Almost surely, 2^9999721872 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 9999721872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16229229120).

9999721872 is an abundant number, since it is smaller than the sum of its proper divisors (22458736368).

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

9999721872 is a wasteful number, since it uses less digits than its factorization.

9999721872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 710 (or 701 counting only the distinct ones).

The product of its digits is 10287648, while the sum is 63.

The square root of 9999721872 is about 99998.6093503305. The cubic root of 9999721872 is about 2154.4147162263.

The spelling of 9999721872 in words is "nine billion, nine hundred ninety-nine million, seven hundred twenty-one thousand, eight hundred seventy-two".