221920609 has 3 divisors (see below), whose sum is σ = 221935507. Its totient is φ = 221905712.

The previous prime is 221920603. The next prime is 221920613. The reversal of 221920609 is 906029122.

The square root of 221920609 is 14897.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 206928225 + 14992384 = 14385^2 + 3872^2 .

It is not a de Polignac number, because 221920609 - 2¹⁷ = 221789537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221920603) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 7449 + ... + 22345.

Almost surely, 2^221920609 is an apocalyptic number.

221920609 is the 14897-th square number.

221920609 is the 7449-th centered octagonal number.

It is an amenable number.

221920609 is a deficient number, since it is larger than the sum of its proper divisors (14898).

221920609 is an frugal number, since it uses more digits than its factorization.

221920609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29794 (or 14897 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 31.

The cubic root of 221920609 is about 605.4327064069.

The spelling of 221920609 in words is "two hundred twenty-one million, nine hundred twenty thousand, six hundred nine".