9971721 has 16 divisors (see below), whose sum is σ = 14884800. Its totient is φ = 6597504.

The previous prime is 9971711. The next prime is 9971729. The reversal of 9971721 is 1271799.

It is not a de Polignac number, because 9971721 - 2⁹ = 9971209 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (9971729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2425 + ... + 5081.

It is an arithmetic number, because the mean of its divisors is an integer number (930300).

Almost surely, 2^9971721 is an apocalyptic number.

It is an amenable number.

9971721 is a deficient number, since it is larger than the sum of its proper divisors (4913079).

9971721 is a wasteful number, since it uses less digits than its factorization.

9971721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2805 (or 2799 counting only the distinct ones).

The product of its digits is 7938, while the sum is 36.

The square root of 9971721 is about 3157.8031920941. The cubic root of 9971721 is about 215.2401930726.

The spelling of 9971721 in words is "nine million, nine hundred seventy-one thousand, seven hundred twenty-one".