221212321 has 24 divisors (see below), whose sum is σ = 256560192. Its totient is φ = 190212000.

The previous prime is 221212309. The next prime is 221212333. The reversal of 221212321 is 123212122.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (221212309) and next prime (221212333).

It is not a de Polignac number, because 221212321 - 2¹³ = 221204129 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221212295 and 221212304.

It is not an unprimeable number, because it can be changed into a prime (221212351) 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, 280690 + ... + 281476.

It is an arithmetic number, because the mean of its divisors is an integer number (10690008).

Almost surely, 2^221212321 is an apocalyptic number.

It is an amenable number.

221212321 is a deficient number, since it is larger than the sum of its proper divisors (35347871).

221212321 is a wasteful number, since it uses less digits than its factorization.

221212321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 933 (or 922 counting only the distinct ones).

The product of its digits is 96, while the sum is 16.

The square root of 221212321 is about 14873.2081609853. The cubic root of 221212321 is about 604.7879146420.

Adding to 221212321 its reverse (123212122), we get a palindrome (344424443).

It can be divided in two parts, 22121 and 2321, that added together give a palindrome (24442).

The spelling of 221212321 in words is "two hundred twenty-one million, two hundred twelve thousand, three hundred twenty-one".