9721721 has 2 divisors, whose sum is σ = 9721722. Its totient is φ = 9721720.

The previous prime is 9721717. The next prime is 9721727. The reversal of 9721721 is 1271279.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9703225 + 18496 = 3115^2 + 136^2 .

It is a cyclic number.

It is not a de Polignac number, because 9721721 - 2² = 9721717 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (9721727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4860860 + 4860861.

It is an arithmetic number, because the mean of its divisors is an integer number (4860861).

Almost surely, 2^9721721 is an apocalyptic number.

It is an amenable number.

9721721 is a deficient number, since it is larger than the sum of its proper divisors (1).

9721721 is an equidigital number, since it uses as much as digits as its factorization.

9721721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1764, while the sum is 29.

The square root of 9721721 is about 3117.9674469115. The cubic root of 9721721 is about 213.4261930269.

The spelling of 9721721 in words is "nine million, seven hundred twenty-one thousand, seven hundred twenty-one".