9721728 has 128 divisors (see below), whose sum is σ = 29988000. Its totient is φ = 3096576.

The previous prime is 9721727. The next prime is 9721759. The reversal of 9721728 is 8271279.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-3 number, since 3×9721728³ (a number of 22 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 9721692 and 9721701.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9721721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 100176 + ... + 100272.

Almost surely, 2^9721728 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 9721728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (14994000).

9721728 is an abundant number, since it is smaller than the sum of its proper divisors (20266272).

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

9721728 is a wasteful number, since it uses less digits than its factorization.

9721728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 149 (or 131 counting only the distinct ones).

The product of its digits is 14112, while the sum is 36.

The square root of 9721728 is about 3117.9685694375. The cubic root of 9721728 is about 213.4262442518.

It can be divided in two parts, 972 and 1728, that multiplied together give a 8-th power (1679616 = 6⁸).

The spelling of 9721728 in words is "nine million, seven hundred twenty-one thousand, seven hundred twenty-eight".