221566 has 8 divisors (see below), whose sum is σ = 335160. Its totient is φ = 109848.

The previous prime is 221549. The next prime is 221567. The reversal of 221566 is 665122.

221566 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221567) by changing a digit.

221566 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 121 + ... + 676.

It is an arithmetic number, because the mean of its divisors is an integer number (41895).

2²²¹⁵⁶⁶ is an apocalyptic number.

221566 is a deficient number, since it is larger than the sum of its proper divisors (113594).

221566 is a wasteful number, since it uses less digits than its factorization.

221566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 938.

The product of its digits is 720, while the sum is 22.

The square root of 221566 is about 470.7079774127. The cubic root of 221566 is about 60.5110058979.

Adding to 221566 its reverse (665122), we get a palindrome (886688).

Subtracting 221566 from its reverse (665122), we obtain a square (443556 = 666²).

It can be divided in two parts, 221 and 566, that added together give a palindrome (787).

The spelling of 221566 in words is "two hundred twenty-one thousand, five hundred sixty-six".