221539909 has 2 divisors, whose sum is σ = 221539910. Its totient is φ = 221539908.

The previous prime is 221539907. The next prime is 221539963. The reversal of 221539909 is 909935122.

221539909 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., 218389284 + 3150625 = 14778^2 + 1775^2 .

It is a cyclic number.

It is not a de Polignac number, because 221539909 - 2¹ = 221539907 is a prime.

Together with 221539907, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221539907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110769954 + 110769955.

It is an arithmetic number, because the mean of its divisors is an integer number (110769955).

Almost surely, 2^221539909 is an apocalyptic number.

It is an amenable number.

221539909 is a deficient number, since it is larger than the sum of its proper divisors (1).

221539909 is an equidigital number, since it uses as much as digits as its factorization.

221539909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 43740, while the sum is 40.

The square root of 221539909 is about 14884.2167748256. The cubic root of 221539909 is about 605.0863060173.

It can be divided in two parts, 2215 and 39909, that added together give a palindrome (42124).

The spelling of 221539909 in words is "two hundred twenty-one million, five hundred thirty-nine thousand, nine hundred nine".