209868221 has 4 divisors (see below), whose sum is σ = 210037500. Its totient is φ = 209698944.

The previous prime is 209868209. The next prime is 209868227. The reversal of 209868221 is 122868902.

209868221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in 2 ways, for example, as 88096996 + 121771225 = 9386^2 + 11035^2 .

It is a cyclic number.

It is not a de Polignac number, because 209868221 - 2¹⁰ = 209867197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209868227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82766 + ... + 85263.

It is an arithmetic number, because the mean of its divisors is an integer number (52509375).

Almost surely, 2^209868221 is an apocalyptic number.

It is an amenable number.

209868221 is a deficient number, since it is larger than the sum of its proper divisors (169279).

209868221 is a wasteful number, since it uses less digits than its factorization.

209868221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 169278.

The product of its (nonzero) digits is 27648, while the sum is 38.

The square root of 209868221 is about 14486.8292251962. The cubic root of 209868221 is about 594.2678384525.

The spelling of 209868221 in words is "two hundred nine million, eight hundred sixty-eight thousand, two hundred twenty-one".