221320561 has 16 divisors (see below), whose sum is σ = 279825408. Its totient is φ = 170024400.

The previous prime is 221320553. The next prime is 221320573. The reversal of 221320561 is 165023122.

It is not a de Polignac number, because 221320561 - 2³ = 221320553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221320511) 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 15 ways as a sum of consecutive naturals, for example, 14775 + ... + 25708.

It is an arithmetic number, because the mean of its divisors is an integer number (17489088).

Almost surely, 2^221320561 is an apocalyptic number.

It is an amenable number.

221320561 is a deficient number, since it is larger than the sum of its proper divisors (58504847).

221320561 is a wasteful number, since it uses less digits than its factorization.

221320561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40572.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 221320561 is about 14876.8464736314. The cubic root of 221320561 is about 604.8865402060.

Adding to 221320561 its reverse (165023122), we get a palindrome (386343683).

The spelling of 221320561 in words is "two hundred twenty-one million, three hundred twenty thousand, five hundred sixty-one".