1221311209 has 2 divisors, whose sum is σ = 1221311210. Its totient is φ = 1221311208.

The previous prime is 1221311159. The next prime is 1221311213. The reversal of 1221311209 is 9021131221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 714385984 + 506925225 = 26728^2 + 22515^2 .

It is an emirp because it is prime and its reverse (9021131221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221311209 - 2⁷ = 1221311081 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1221311209.

It is not a weakly prime, because it can be changed into another prime (1221315209) 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, 610655604 + 610655605.

It is an arithmetic number, because the mean of its divisors is an integer number (610655605).

Almost surely, 2^1221311209 is an apocalyptic number.

It is an amenable number.

1221311209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221311209 is an equidigital number, since it uses as much as digits as its factorization.

1221311209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 216, while the sum is 22.

The square root of 1221311209 is about 34947.2632547958. The cubic root of 1221311209 is about 1068.9123979525.

The spelling of 1221311209 in words is "one billion, two hundred twenty-one million, three hundred eleven thousand, two hundred nine".