221905 has 4 divisors (see below), whose sum is σ = 266292. Its totient is φ = 177520.

The previous prime is 221891. The next prime is 221909. The reversal of 221905 is 509122.

221905 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 83521 + 138384 = 289^2 + 372^2 .

It is not a de Polignac number, because 221905 - 2⁵ = 221873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221909) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22186 + ... + 22195.

It is an arithmetic number, because the mean of its divisors is an integer number (66573).

2²²¹⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

221905 is a deficient number, since it is larger than the sum of its proper divisors (44387).

221905 is an equidigital number, since it uses as much as digits as its factorization.

221905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44386.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 221905 is about 471.0679356526. The cubic root of 221905 is about 60.5418511510.

The spelling of 221905 in words is "two hundred twenty-one thousand, nine hundred five".