8720403721 has 2 divisors, whose sum is σ = 8720403722. Its totient is φ = 8720403720.

The previous prime is 8720403709. The next prime is 8720403737. The reversal of 8720403721 is 1273040278.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7589023225 + 1131380496 = 87115^2 + 33636^2 .

It is a cyclic number.

It is not a de Polignac number, because 8720403721 - 2⁵ = 8720403689 is a prime.

It is not a weakly prime, because it can be changed into another prime (8720403781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4360201860 + 4360201861.

It is an arithmetic number, because the mean of its divisors is an integer number (4360201861).

Almost surely, 2^8720403721 is an apocalyptic number.

It is an amenable number.

8720403721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8720403721 is an equidigital number, since it uses as much as digits as its factorization.

8720403721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18816, while the sum is 34.

The square root of 8720403721 is about 93383.1019028603. The cubic root of 8720403721 is about 2058.3166976701.

Adding to 8720403721 its reverse (1273040278), we get a palindrome (9993443999).

The spelling of 8720403721 in words is "eight billion, seven hundred twenty million, four hundred three thousand, seven hundred twenty-one".