6728928721 has 2 divisors, whose sum is σ = 6728928722. Its totient is φ = 6728928720.

The previous prime is 6728928697. The next prime is 6728928761. The reversal of 6728928721 is 1278298276.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4075545600 + 2653383121 = 63840^2 + 51511^2 .

It is a cyclic number.

It is not a de Polignac number, because 6728928721 - 2²¹ = 6726831569 is a prime.

It is not a weakly prime, because it can be changed into another prime (6728928761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3364464360 + 3364464361.

It is an arithmetic number, because the mean of its divisors is an integer number (3364464361).

Almost surely, 2^6728928721 is an apocalyptic number.

It is an amenable number.

6728928721 is a deficient number, since it is larger than the sum of its proper divisors (1).

6728928721 is an equidigital number, since it uses as much as digits as its factorization.

6728928721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1354752, while the sum is 52.

The square root of 6728928721 is about 82030.0476715697. The cubic root of 6728928721 is about 1887.9129955216.

The spelling of 6728928721 in words is "six billion, seven hundred twenty-eight million, nine hundred twenty-eight thousand, seven hundred twenty-one".