721705211321 has 2 divisors, whose sum is σ = 721705211322. Its totient is φ = 721705211320.

The previous prime is 721705211309. The next prime is 721705211329. The reversal of 721705211321 is 123112507127.

721705211321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 712444036096 + 9261175225 = 844064^2 + 96235^2 .

It is a cyclic number.

It is not a de Polignac number, because 721705211321 - 2¹⁰ = 721705210297 is a prime.

It is not a weakly prime, because it can be changed into another prime (721705211329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360852605660 + 360852605661.

It is an arithmetic number, because the mean of its divisors is an integer number (360852605661).

Almost surely, 2^721705211321 is an apocalyptic number.

It is an amenable number.

721705211321 is a deficient number, since it is larger than the sum of its proper divisors (1).

721705211321 is an equidigital number, since it uses as much as digits as its factorization.

721705211321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5880, while the sum is 32.

Adding to 721705211321 its reverse (123112507127), we get a palindrome (844817718448).

The spelling of 721705211321 in words is "seven hundred twenty-one billion, seven hundred five million, two hundred eleven thousand, three hundred twenty-one".