165221209 has 2 divisors, whose sum is σ = 165221210. Its totient is φ = 165221208.

The previous prime is 165221197. The next prime is 165221237. The reversal of 165221209 is 902122561.

165221209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (165221237) can be obtained adding 165221209 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 131905225 + 33315984 = 11485^2 + 5772^2 .

It is a cyclic number.

It is not a de Polignac number, because 165221209 - 2¹¹ = 165219161 is a prime.

It is not a weakly prime, because it can be changed into another prime (165228209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82610604 + 82610605.

It is an arithmetic number, because the mean of its divisors is an integer number (82610605).

Almost surely, 2^165221209 is an apocalyptic number.

It is an amenable number.

165221209 is a deficient number, since it is larger than the sum of its proper divisors (1).

165221209 is an equidigital number, since it uses as much as digits as its factorization.

165221209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 165221209 is about 12853.8402432892. The cubic root of 165221209 is about 548.7256545914.

It can be divided in two parts, 16 and 5221209, that added together give a palindrome (5221225).

The spelling of 165221209 in words is "one hundred sixty-five million, two hundred twenty-one thousand, two hundred nine".