212121209 has 2 divisors, whose sum is σ = 212121210. Its totient is φ = 212121208.

The previous prime is 212121197. The next prime is 212121289. The reversal of 212121209 is 902121212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 198021184 + 14100025 = 14072^2 + 3755^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-212121209 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (212121289) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106060604 + 106060605.

It is an arithmetic number, because the mean of its divisors is an integer number (106060605).

Almost surely, 2^212121209 is an apocalyptic number.

It is an amenable number.

212121209 is a deficient number, since it is larger than the sum of its proper divisors (1).

212121209 is an equidigital number, since it uses as much as digits as its factorization.

212121209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 212121209 is about 14564.3815179361. The cubic root of 212121209 is about 596.3868119823.

The spelling of 212121209 in words is "two hundred twelve million, one hundred twenty-one thousand, two hundred nine".