221561321 has 2 divisors, whose sum is σ = 221561322. Its totient is φ = 221561320.

The previous prime is 221561311. The next prime is 221561381. The reversal of 221561321 is 123165122.

221561321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 197009296 + 24552025 = 14036^2 + 4955^2 .

It is a cyclic number.

It is not a de Polignac number, because 221561321 - 2⁶ = 221561257 is a prime.

It is not a weakly prime, because it can be changed into another prime (221561311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110780660 + 110780661.

It is an arithmetic number, because the mean of its divisors is an integer number (110780661).

Almost surely, 2^221561321 is an apocalyptic number.

It is an amenable number.

221561321 is a deficient number, since it is larger than the sum of its proper divisors (1).

221561321 is an equidigital number, since it uses as much as digits as its factorization.

221561321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 720, while the sum is 23.

The square root of 221561321 is about 14884.9360428589. The cubic root of 221561321 is about 605.1057994059.

It can be divided in two parts, 2215 and 61321, that added together give a palindrome (63536).

The spelling of 221561321 in words is "two hundred twenty-one million, five hundred sixty-one thousand, three hundred twenty-one".