221609 has 4 divisors (see below), whose sum is σ = 223104. Its totient is φ = 220116.

The previous prime is 221603. The next prime is 221621. The reversal of 221609 is 906122.

221609 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, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221609 is a prime.

It is a super-2 number, since 2×221609² = 98221097762, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a plaindrome in base 15.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 221609.

It is not an unprimeable number, because it can be changed into a prime (221603) 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, 497 + ... + 830.

It is an arithmetic number, because the mean of its divisors is an integer number (55776).

2²²¹⁶⁰⁹ is an apocalyptic number.

It is an amenable number.

221609 is a deficient number, since it is larger than the sum of its proper divisors (1495).

221609 is a wasteful number, since it uses less digits than its factorization.

221609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1494.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 221609 is about 470.7536510745. The cubic root of 221609 is about 60.5149201642.

The spelling of 221609 in words is "two hundred twenty-one thousand, six hundred nine".