221639 has 4 divisors (see below), whose sum is σ = 241800. Its totient is φ = 201480.

The previous prime is 221623. The next prime is 221653. The reversal of 221639 is 936122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221639 - 2⁴ = 221623 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221659) 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, 10064 + ... + 10085.

It is an arithmetic number, because the mean of its divisors is an integer number (60450).

2²²¹⁶³⁹ is an apocalyptic number.

221639 is a deficient number, since it is larger than the sum of its proper divisors (20161).

221639 is a wasteful number, since it uses less digits than its factorization.

221639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20160.

The product of its digits is 648, while the sum is 23.

The square root of 221639 is about 470.7855137958. The cubic root of 221639 is about 60.5176507478.

It can be divided in two parts, 22 and 1639, that added together give a palindrome (1661).

The spelling of 221639 in words is "two hundred twenty-one thousand, six hundred thirty-nine".