9820721 has 2 divisors, whose sum is σ = 9820722. Its totient is φ = 9820720.

The previous prime is 9820703. The next prime is 9820729. The reversal of 9820721 is 1270289.

It is a happy number.

9820721 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., 9241600 + 579121 = 3040^2 + 761^2 .

It is a cyclic number.

It is not a de Polignac number, because 9820721 - 2¹⁰ = 9819697 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9820729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4910360 + 4910361.

It is an arithmetic number, because the mean of its divisors is an integer number (4910361).

Almost surely, 2^9820721 is an apocalyptic number.

It is an amenable number.

9820721 is a deficient number, since it is larger than the sum of its proper divisors (1).

9820721 is an equidigital number, since it uses as much as digits as its factorization.

9820721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 9820721 is about 3133.8029612597. The cubic root of 9820721 is about 214.1482144990.

The spelling of 9820721 in words is "nine million, eight hundred twenty thousand, seven hundred twenty-one".