221605 has 16 divisors (see below), whose sum is σ = 290304. Its totient is φ = 161920.

The previous prime is 221603. The next prime is 221621. The reversal of 221605 is 506122.

It is a happy number.

221605 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 221605 - 2¹ = 221603 is a prime.

It is a Duffinian number.

221605 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221603) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4692 + ... + 4738.

It is an arithmetic number, because the mean of its divisors is an integer number (18144).

2²²¹⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

221605 is a deficient number, since it is larger than the sum of its proper divisors (68699).

221605 is a wasteful number, since it uses less digits than its factorization.

221605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 221605 is about 470.7494025487. The cubic root of 221605 is about 60.5145560677.

Adding to 221605 its reverse (506122), we get a palindrome (727727).

The spelling of 221605 in words is "two hundred twenty-one thousand, six hundred five".