728922721 has 2 divisors, whose sum is σ = 728922722. Its totient is φ = 728922720.

The previous prime is 728922709. The next prime is 728922737. The reversal of 728922721 is 127229827.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 689797696 + 39125025 = 26264^2 + 6255^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-728922721 is a prime.

It is not a weakly prime, because it can be changed into another prime (728922421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 364461360 + 364461361.

It is an arithmetic number, because the mean of its divisors is an integer number (364461361).

Almost surely, 2^728922721 is an apocalyptic number.

It is an amenable number.

728922721 is a deficient number, since it is larger than the sum of its proper divisors (1).

728922721 is an equidigital number, since it uses as much as digits as its factorization.

728922721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56448, while the sum is 40.

The square root of 728922721 is about 26998.5688694790. The cubic root of 728922721 is about 899.9681968186.

The spelling of 728922721 in words is "seven hundred twenty-eight million, nine hundred twenty-two thousand, seven hundred twenty-one".