221401666 has 4 divisors (see below), whose sum is σ = 332102502. Its totient is φ = 110700832.

The previous prime is 221401637. The next prime is 221401709. The reversal of 221401666 is 666104122.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 221146641 + 255025 = 14871^2 + 505^2 .

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 55350415 + ... + 55350418.

Almost surely, 2^221401666 is an apocalyptic number.

221401666 is a deficient number, since it is larger than the sum of its proper divisors (110700836).

221401666 is a wasteful number, since it uses less digits than its factorization.

221401666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110700835.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 221401666 is about 14879.5721040627. The cubic root of 221401666 is about 604.9604199683.

Adding to 221401666 its reverse (666104122), we get a palindrome (887505788).

The spelling of 221401666 in words is "two hundred twenty-one million, four hundred one thousand, six hundred sixty-six".