221864 has 8 divisors (see below), whose sum is σ = 416010. Its totient is φ = 110928.

The previous prime is 221849. The next prime is 221873. The reversal of 221864 is 468122.

It can be written as a sum of positive squares in only one way, i.e., 209764 + 12100 = 458^2 + 110^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

221864 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13859 + ... + 13874.

2²²¹⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

221864 is a deficient number, since it is larger than the sum of its proper divisors (194146).

221864 is a wasteful number, since it uses less digits than its factorization.

221864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27739 (or 27735 counting only the distinct ones).

The product of its digits is 768, while the sum is 23.

The square root of 221864 is about 471.0244155031. The cubic root of 221864 is about 60.5381222748.

Subtracting from 221864 its sum of digits (23), we obtain a square (221841 = 471²).

Adding to 221864 its reverse (468122), we get a palindrome (689986).

The spelling of 221864 in words is "two hundred twenty-one thousand, eight hundred sixty-four".