9721981 has 4 divisors (see below), whose sum is σ = 9742432. Its totient is φ = 9701532.

The previous prime is 9721979. The next prime is 9721991. The reversal of 9721981 is 1891279.

9721981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 9721981 - 2¹ = 9721979 is a prime.

It is a super-2 number, since 2×9721981² = 189033829128722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 9721981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9721951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9495 + ... + 10468.

It is an arithmetic number, because the mean of its divisors is an integer number (2435608).

Almost surely, 2^9721981 is an apocalyptic number.

It is an amenable number.

9721981 is a deficient number, since it is larger than the sum of its proper divisors (20451).

9721981 is a wasteful number, since it uses less digits than its factorization.

9721981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20450.

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

The square root of 9721981 is about 3118.0091404613. The cubic root of 9721981 is about 213.4280956501.

The spelling of 9721981 in words is "nine million, seven hundred twenty-one thousand, nine hundred eighty-one".