221641666 has 8 divisors (see below), whose sum is σ = 333204300. Its totient is φ = 110573568.

The previous prime is 221641643. The next prime is 221641681. The reversal of 221641666 is 666146122.

It can be written as a sum of positive squares in 2 ways, for example, as 213773641 + 7868025 = 14621^2 + 2805^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122511 + ... + 124306.

Almost surely, 2^221641666 is an apocalyptic number.

221641666 is a deficient number, since it is larger than the sum of its proper divisors (111562634).

221641666 is a wasteful number, since it uses less digits than its factorization.

221641666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 247268.

The product of its digits is 20736, while the sum is 34.

The square root of 221641666 is about 14887.6346677368. The cubic root of 221641666 is about 605.1789339369.

Adding to 221641666 its reverse (666146122), we get a palindrome (887787788).

The spelling of 221641666 in words is "two hundred twenty-one million, six hundred forty-one thousand, six hundred sixty-six".