121721209 has 2 divisors, whose sum is σ = 121721210. Its totient is φ = 121721208.

The previous prime is 121721203. The next prime is 121721219. The reversal of 121721209 is 902127121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 111767184 + 9954025 = 10572^2 + 3155^2 .

It is a cyclic number.

It is not a de Polignac number, because 121721209 - 2¹¹ = 121719161 is a prime.

It is not a weakly prime, because it can be changed into another prime (121721203) by changing a digit.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 60860604 + 60860605.

It is an arithmetic number, because the mean of its divisors is an integer number (60860605).

Almost surely, 2^121721209 is an apocalyptic number.

It is an amenable number.

121721209 is a deficient number, since it is larger than the sum of its proper divisors (1).

121721209 is an equidigital number, since it uses as much as digits as its factorization.

121721209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 504, while the sum is 25.

The square root of 121721209 is about 11032.7335234746. The cubic root of 121721209 is about 495.5894878261.

The spelling of 121721209 in words is "one hundred twenty-one million, seven hundred twenty-one thousand, two hundred nine".