9916721 has 4 divisors (see below), whose sum is σ = 9924132. Its totient is φ = 9909312.

The previous prime is 9916691. The next prime is 9916723. The reversal of 9916721 is 1276199.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1276199 = 307 ⋅4157.

It can be written as a sum of positive squares in 2 ways, for example, as 583696 + 9333025 = 764^2 + 3055^2 .

It is a cyclic number.

It is not a de Polignac number, because 9916721 - 2¹⁸ = 9654577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9916723) 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, 1076 + ... + 4581.

It is an arithmetic number, because the mean of its divisors is an integer number (2481033).

Almost surely, 2^9916721 is an apocalyptic number.

It is an amenable number.

9916721 is a deficient number, since it is larger than the sum of its proper divisors (7411).

9916721 is a wasteful number, since it uses less digits than its factorization.

9916721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7410.

The product of its digits is 6804, while the sum is 35.

The square root of 9916721 is about 3149.0825648115. The cubic root of 9916721 is about 214.8437371852.

The spelling of 9916721 in words is "nine million, nine hundred sixteen thousand, seven hundred twenty-one".