221205866 has 32 divisors (see below), whose sum is σ = 400152960. Its totient is φ = 89591616.

The previous prime is 221205827. The next prime is 221205877. The reversal of 221205866 is 668502122.

221205866 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a super-3 number, since 3×221205866³ (a number of 26 digits) contains 333 as substring.

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, 147416 + ... + 148908.

It is an arithmetic number, because the mean of its divisors is an integer number (12504780).

Almost surely, 2^221205866 is an apocalyptic number.

221205866 is a deficient number, since it is larger than the sum of its proper divisors (178947094).

221205866 is a wasteful number, since it uses less digits than its factorization.

221205866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2078.

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 221205866 is about 14872.9911584725. The cubic root of 221205866 is about 604.7820319920.

Adding to 221205866 its reverse (668502122), we get a palindrome (889707988).

The spelling of 221205866 in words is "two hundred twenty-one million, two hundred five thousand, eight hundred sixty-six".