221261665 has 16 divisors (see below), whose sum is σ = 278502912. Its totient is φ = 168554304.

The previous prime is 221261641. The next prime is 221261687. The reversal of 221261665 is 566162122.

It is a cyclic number.

It is not a de Polignac number, because 221261665 - 2⁹ = 221261153 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4029 + ... + 21418.

It is an arithmetic number, because the mean of its divisors is an integer number (17406432).

Almost surely, 2^221261665 is an apocalyptic number.

It is an amenable number.

221261665 is a deficient number, since it is larger than the sum of its proper divisors (57241247).

221261665 is a wasteful number, since it uses less digits than its factorization.

221261665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25536.

The product of its digits is 8640, while the sum is 31.

The square root of 221261665 is about 14874.8668901607. The cubic root of 221261665 is about 604.8328796422.

The spelling of 221261665 in words is "two hundred twenty-one million, two hundred sixty-one thousand, six hundred sixty-five".