121805209 has 2 divisors, whose sum is σ = 121805210. Its totient is φ = 121805208.

The previous prime is 121805141. The next prime is 121805237. The reversal of 121805209 is 902508121.

It is an a-pointer prime, because the next prime (121805237) can be obtained adding 121805209 to its sum of digits (28).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 100902025 + 20903184 = 10045^2 + 4572^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-121805209 is a prime.

It is not a weakly prime, because it can be changed into another prime (121805279) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 60902604 + 60902605.

It is an arithmetic number, because the mean of its divisors is an integer number (60902605).

Almost surely, 2^121805209 is an apocalyptic number.

It is an amenable number.

121805209 is a deficient number, since it is larger than the sum of its proper divisors (1).

121805209 is an equidigital number, since it uses as much as digits as its factorization.

121805209 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 28.

The square root of 121805209 is about 11036.5397204015. The cubic root of 121805209 is about 495.7034639764.

The spelling of 121805209 in words is "one hundred twenty-one million, eight hundred five thousand, two hundred nine".