9217721 has 2 divisors, whose sum is σ = 9217722. Its totient is φ = 9217720.

The previous prime is 9217711. The next prime is 9217727. The reversal of 9217721 is 1277129.

9217721 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., 7155625 + 2062096 = 2675^2 + 1436^2 .

It is a cyclic number.

It is not a de Polignac number, because 9217721 - 2⁶ = 9217657 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (9217727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4608860 + 4608861.

It is an arithmetic number, because the mean of its divisors is an integer number (4608861).

Almost surely, 2^9217721 is an apocalyptic number.

It is an amenable number.

9217721 is a deficient number, since it is larger than the sum of its proper divisors (1).

9217721 is an equidigital number, since it uses as much as digits as its factorization.

9217721 is an evil number, because the sum of its binary digits is even.

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

The square root of 9217721 is about 3036.0699926056. The cubic root of 9217721 is about 209.6723613493.

The spelling of 9217721 in words is "nine million, two hundred seventeen thousand, seven hundred twenty-one".