221221 has 24 divisors (see below), whose sum is σ = 316224. Its totient is φ = 149760.

The previous prime is 221219. The next prime is 221227. The reversal of 221221 is 122122.

It is not a de Polignac number, because 221221 - 2¹ = 221219 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221198 and 221207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221227) 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 23 ways as a sum of consecutive naturals, for example, 13005 + ... + 13021.

It is an arithmetic number, because the mean of its divisors is an integer number (13176).

2²²¹²²¹ is an apocalyptic number.

It is an amenable number.

221221 is a deficient number, since it is larger than the sum of its proper divisors (95003).

221221 is a wasteful number, since it uses less digits than its factorization.

221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61 (or 48 counting only the distinct ones).

The product of its digits is 16, while the sum is 10.

The square root of 221221 is about 470.3413653933. The cubic root of 221221 is about 60.4795823915.

Adding to 221221 its reverse (122122), we get a palindrome (343343).

Subtracting from 221221 its reverse (122122), we obtain a palindrome (99099).

It can be divided in two parts, 22 and 1221, that multiplied together give a palindrome (26862).

The spelling of 221221 in words is "two hundred twenty-one thousand, two hundred twenty-one", and thus it is an iban number.