221689 has 4 divisors (see below), whose sum is σ = 238756. Its totient is φ = 204624.

The previous prime is 221677. The next prime is 221707. The reversal of 221689 is 986122.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 55225 + 166464 = 235^2 + 408^2 .

It is a cyclic number.

It is not a de Polignac number, because 221689 - 2⁵ = 221657 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 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, 8514 + ... + 8539.

It is an arithmetic number, because the mean of its divisors is an integer number (59689).

2²²¹⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

221689 is a deficient number, since it is larger than the sum of its proper divisors (17067).

221689 is a wasteful number, since it uses less digits than its factorization.

221689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17066.

The product of its digits is 1728, while the sum is 28.

The square root of 221689 is about 470.8386135397. The cubic root of 221689 is about 60.5222011729.

Subtracting from 221689 its product of digits (1728), we obtain a square (219961 = 469²).

It can be divided in two parts, 22 and 1689, that added together give a triangular number (1711 = T₅₈).

The spelling of 221689 in words is "two hundred twenty-one thousand, six hundred eighty-nine".