221909 has 2 divisors, whose sum is σ = 221910. Its totient is φ = 221908.

The previous prime is 221891. The next prime is 221941. The reversal of 221909 is 909122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 207025 + 14884 = 455^2 + 122^2 .

It is a cyclic number.

It is not a de Polignac number, because 221909 - 2⁸ = 221653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110954 + 110955.

It is an arithmetic number, because the mean of its divisors is an integer number (110955).

2²²¹⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

221909 is a deficient number, since it is larger than the sum of its proper divisors (1).

221909 is an equidigital number, since it uses as much as digits as its factorization.

221909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 221909 is about 471.0721813056. The cubic root of 221909 is about 60.5422149192.

The spelling of 221909 in words is "two hundred twenty-one thousand, nine hundred nine".