209791221 has 16 divisors (see below), whose sum is σ = 293401344. Its totient is φ = 133182144.

The previous prime is 209791207. The next prime is 209791243. The reversal of 209791221 is 122197902.

It is not a de Polignac number, because 209791221 - 2⁵ = 209791189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209711221) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14890 + ... + 25323.

It is an arithmetic number, because the mean of its divisors is an integer number (18337584).

Almost surely, 2^209791221 is an apocalyptic number.

It is an amenable number.

209791221 is a deficient number, since it is larger than the sum of its proper divisors (83610123).

209791221 is a wasteful number, since it uses less digits than its factorization.

209791221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40300.

The product of its (nonzero) digits is 4536, while the sum is 33.

The square root of 209791221 is about 14484.1713950091. The cubic root of 209791221 is about 594.1951512193.

It can be divided in two parts, 209791 and 221, that added together give a palindrome (210012).

The spelling of 209791221 in words is "two hundred nine million, seven hundred ninety-one thousand, two hundred twenty-one".