9781221 has 4 divisors (see below), whose sum is σ = 13041632. Its totient is φ = 6520812.

The previous prime is 9781201. The next prime is 9781223. The reversal of 9781221 is 1221879.

9781221 is digitally balanced in base 3, 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 not a de Polignac number, because 9781221 - 2⁶ = 9781157 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9781223) 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, 1630201 + ... + 1630206.

It is an arithmetic number, because the mean of its divisors is an integer number (3260408).

Almost surely, 2^9781221 is an apocalyptic number.

It is an amenable number.

9781221 is a deficient number, since it is larger than the sum of its proper divisors (3260411).

9781221 is a wasteful number, since it uses less digits than its factorization.

9781221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3260410.

The product of its digits is 2016, while the sum is 30.

The square root of 9781221 is about 3127.4943645033. The cubic root of 9781221 is about 213.8607196300.

It can be divided in two parts, 97 and 81221, that added together give a palindrome (81318).

The spelling of 9781221 in words is "nine million, seven hundred eighty-one thousand, two hundred twenty-one".