9981721 has 4 divisors (see below), whose sum is σ = 10303744. Its totient is φ = 9659700.

The previous prime is 9981691. The next prime is 9981731. The reversal of 9981721 is 1271899.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 9981721 - 2⁵ = 9981689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9981731) 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 3 ways as a sum of consecutive naturals, for example, 160965 + ... + 161026.

It is an arithmetic number, because the mean of its divisors is an integer number (2575936).

Almost surely, 2^9981721 is an apocalyptic number.

It is an amenable number.

9981721 is a deficient number, since it is larger than the sum of its proper divisors (322023).

9981721 is a wasteful number, since it uses less digits than its factorization.

9981721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322022.

The product of its digits is 9072, while the sum is 37.

The square root of 9981721 is about 3159.3861745599. The cubic root of 9981721 is about 215.3121192336.

The spelling of 9981721 in words is "nine million, nine hundred eighty-one thousand, seven hundred twenty-one".