9721521 has 24 divisors (see below), whose sum is σ = 14924000. Its totient is φ = 6080832.

The previous prime is 9721519. The next prime is 9721529. The reversal of 9721521 is 1251279.

It is not a de Polignac number, because 9721521 - 2¹ = 9721519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9721529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 23565 + ... + 23973.

Almost surely, 2^9721521 is an apocalyptic number.

It is an amenable number.

9721521 is a deficient number, since it is larger than the sum of its proper divisors (5202479).

9721521 is a wasteful number, since it uses less digits than its factorization.

9721521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 573 (or 570 counting only the distinct ones).

The product of its digits is 1260, while the sum is 27.

The square root of 9721521 is about 3117.9353745708. The cubic root of 9721521 is about 213.4247294475.

The spelling of 9721521 in words is "nine million, seven hundred twenty-one thousand, five hundred twenty-one".