221601809 has 16 divisors (see below), whose sum is σ = 261227904. Its totient is φ = 185328000.

The previous prime is 221601791. The next prime is 221601811. The reversal of 221601809 is 908106122.

It is not a de Polignac number, because 221601809 - 2⁸ = 221601553 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (221601859) 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 15 ways as a sum of consecutive naturals, for example, 42284 + ... + 47234.

It is an arithmetic number, because the mean of its divisors is an integer number (16326744).

Almost surely, 2^221601809 is an apocalyptic number.

It is an amenable number.

221601809 is a deficient number, since it is larger than the sum of its proper divisors (39626095).

221601809 is a wasteful number, since it uses less digits than its factorization.

221601809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5288.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 221601809 is about 14886.2960134481. The cubic root of 221601809 is about 605.1426560667.

The spelling of 221601809 in words is "two hundred twenty-one million, six hundred one thousand, eight hundred nine".