728663821 has 2 divisors, whose sum is σ = 728663822. Its totient is φ = 728663820.

The previous prime is 728663791. The next prime is 728663833. The reversal of 728663821 is 128366827.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 586124100 + 142539721 = 24210^2 + 11939^2 .

It is an emirp because it is prime and its reverse (128366827) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-728663821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (728663891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 364331910 + 364331911.

It is an arithmetic number, because the mean of its divisors is an integer number (364331911).

Almost surely, 2^728663821 is an apocalyptic number.

It is an amenable number.

728663821 is a deficient number, since it is larger than the sum of its proper divisors (1).

728663821 is an equidigital number, since it uses as much as digits as its factorization.

728663821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 43.

The square root of 728663821 is about 26993.7737450694. The cubic root of 728663821 is about 899.8616334610.

The spelling of 728663821 in words is "seven hundred twenty-eight million, six hundred sixty-three thousand, eight hundred twenty-one".