221566665 has 16 divisors (see below), whose sum is σ = 363154176. Its totient is φ = 115286400.

The previous prime is 221566621. The next prime is 221566687. The reversal of 221566665 is 566665122.

It is a happy number.

It is not a de Polignac number, because 221566665 - 2⁷ = 221566537 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 179521 + ... + 180750.

It is an arithmetic number, because the mean of its divisors is an integer number (22697136).

Almost surely, 2^221566665 is an apocalyptic number.

It is an amenable number.

221566665 is a deficient number, since it is larger than the sum of its proper divisors (141587511).

221566665 is a wasteful number, since it uses less digits than its factorization.

221566665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360320.

The product of its digits is 129600, while the sum is 39.

The square root of 221566665 is about 14885.1155521212. The cubic root of 221566665 is about 605.1106643636.

The spelling of 221566665 in words is "two hundred twenty-one million, five hundred sixty-six thousand, six hundred sixty-five".