9899721 has 24 divisors (see below), whose sum is σ = 15515136. Its totient is φ = 6046560.

The previous prime is 9899693. The next prime is 9899731. The reversal of 9899721 is 1279989.

9899721 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 9899721 - 2⁵ = 9899689 is a prime.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (9899731) 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, 22126 + ... + 22568.

It is an arithmetic number, because the mean of its divisors is an integer number (646464).

Almost surely, 2^9899721 is an apocalyptic number.

It is an amenable number.

9899721 is a deficient number, since it is larger than the sum of its proper divisors (5615415).

9899721 is a wasteful number, since it uses less digits than its factorization.

9899721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 653 (or 650 counting only the distinct ones).

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

The square root of 9899721 is about 3146.3822081877. The cubic root of 9899721 is about 214.7208997889.

The spelling of 9899721 in words is "nine million, eight hundred ninety-nine thousand, seven hundred twenty-one".