999728321 has 2 divisors, whose sum is σ = 999728322. Its totient is φ = 999728320.

The previous prime is 999728309. The next prime is 999728381. The reversal of 999728321 is 123827999.

999728321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 540097600 + 459630721 = 23240^2 + 21439^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999728321 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 999728321.

It is not a weakly prime, because it can be changed into another prime (999728381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499864160 + 499864161.

It is an arithmetic number, because the mean of its divisors is an integer number (499864161).

Almost surely, 2^999728321 is an apocalyptic number.

It is an amenable number.

999728321 is a deficient number, since it is larger than the sum of its proper divisors (1).

999728321 is an equidigital number, since it uses as much as digits as its factorization.

999728321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 489888, while the sum is 50.

The square root of 999728321 is about 31618.4806877244. The cubic root of 999728321 is about 999.9094321310.

The spelling of 999728321 in words is "nine hundred ninety-nine million, seven hundred twenty-eight thousand, three hundred twenty-one".