209518121 has 2 divisors, whose sum is σ = 209518122. Its totient is φ = 209518120.

The previous prime is 209518097. The next prime is 209518189. The reversal of 209518121 is 121815902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 204061225 + 5456896 = 14285^2 + 2336^2 .

It is a cyclic number.

It is not a de Polignac number, because 209518121 - 2¹⁴ = 209501737 is a prime.

It is not a weakly prime, because it can be changed into another prime (209518721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104759060 + 104759061.

It is an arithmetic number, because the mean of its divisors is an integer number (104759061).

Almost surely, 2^209518121 is an apocalyptic number.

It is an amenable number.

209518121 is a deficient number, since it is larger than the sum of its proper divisors (1).

209518121 is an equidigital number, since it uses as much as digits as its factorization.

209518121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 29.

The square root of 209518121 is about 14474.7407921524. The cubic root of 209518121 is about 593.9372040393.

The spelling of 209518121 in words is "two hundred nine million, five hundred eighteen thousand, one hundred twenty-one".