221866 has 4 divisors (see below), whose sum is σ = 332802. Its totient is φ = 110932.

The previous prime is 221849. The next prime is 221873. The reversal of 221866 is 668122.

221866 is nontrivially palindromic in base 12.

221866 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 only one way, i.e., 221841 + 25 = 471^2 + 5^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 221866.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55465 + ... + 55468.

2²²¹⁸⁶⁶ is an apocalyptic number.

221866 is a deficient number, since it is larger than the sum of its proper divisors (110936).

221866 is a wasteful number, since it uses less digits than its factorization.

221866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110935.

The product of its digits is 1152, while the sum is 25.

The square root of 221866 is about 471.0265385305. The cubic root of 221866 is about 60.5383041819.

Subtracting from 221866 its sum of digits (25), we obtain a square (221841 = 471²).

Adding to 221866 its reverse (668122), we get a palindrome (889988).

The spelling of 221866 in words is "two hundred twenty-one thousand, eight hundred sixty-six".