9998721 has 24 divisors (see below), whose sum is σ = 15637440. Its totient is φ = 6372432.

The previous prime is 9998719. The next prime is 9998741. The reversal of 9998721 is 1278999.

It is not a de Polignac number, because 9998721 - 2¹ = 9998719 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9998701) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4695 + ... + 6483.

It is an arithmetic number, because the mean of its divisors is an integer number (651560).

Almost surely, 2^9998721 is an apocalyptic number.

It is an amenable number.

9998721 is a deficient number, since it is larger than the sum of its proper divisors (5638719).

9998721 is a wasteful number, since it uses less digits than its factorization.

9998721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1827 (or 1815 counting only the distinct ones).

The product of its digits is 81648, while the sum is 45.

The square root of 9998721 is about 3162.0754260454. The cubic root of 9998721 is about 215.4342835383.

The spelling of 9998721 in words is "nine million, nine hundred ninety-eight thousand, seven hundred twenty-one".