221312321 has 4 divisors (see below), whose sum is σ = 221375700. Its totient is φ = 221248944.

The previous prime is 221312303. The next prime is 221312353. The reversal of 221312321 is 123213122.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 120209296 + 101103025 = 10964^2 + 10055^2 .

It is a cyclic number.

It is not a de Polignac number, because 221312321 - 2¹⁴ = 221295937 is a prime.

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 221312321.

It is not an unprimeable number, because it can be changed into a prime (221312921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26126 + ... + 33543.

It is an arithmetic number, because the mean of its divisors is an integer number (55343925).

Almost surely, 2^221312321 is an apocalyptic number.

It is an amenable number.

221312321 is a deficient number, since it is larger than the sum of its proper divisors (63379).

221312321 is an equidigital number, since it uses as much as digits as its factorization.

221312321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63378.

The product of its digits is 144, while the sum is 17.

The square root of 221312321 is about 14876.5695306411. The cubic root of 221312321 is about 604.8790332563.

Adding to 221312321 its reverse (123213122), we get a palindrome (344525443).

The spelling of 221312321 in words is "two hundred twenty-one million, three hundred twelve thousand, three hundred twenty-one".