220721666 has 24 divisors (see below), whose sum is σ = 372397872. Its totient is φ = 97990200.

The previous prime is 220721617. The next prime is 220721681. The reversal of 220721666 is 666127022.

It is a Curzon 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 11 ways as a sum of consecutive naturals, for example, 200 + ... + 21011.

It is an arithmetic number, because the mean of its divisors is an integer number (15516578).

Almost surely, 2^220721666 is an apocalyptic number.

220721666 is a deficient number, since it is larger than the sum of its proper divisors (151676206).

220721666 is a wasteful number, since it uses less digits than its factorization.

220721666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21278 (or 21267 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 32.

The square root of 220721666 is about 14856.7044124866. The cubic root of 220721666 is about 604.3404382419.

Adding to 220721666 its reverse (666127022), we get a palindrome (886848688).

The spelling of 220721666 in words is "two hundred twenty million, seven hundred twenty-one thousand, six hundred sixty-six".