1221161309 has 2 divisors, whose sum is σ = 1221161310. Its totient is φ = 1221161308.

The previous prime is 1221161273. The next prime is 1221161317. The reversal of 1221161309 is 9031611221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 647702500 + 573458809 = 25450^2 + 23947^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221161309 - 2¹⁶ = 1221095773 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221161329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610580654 + 610580655.

It is an arithmetic number, because the mean of its divisors is an integer number (610580655).

Almost surely, 2^1221161309 is an apocalyptic number.

It is an amenable number.

1221161309 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221161309 is an equidigital number, since it uses as much as digits as its factorization.

1221161309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 1221161309 is about 34945.1185289162. The cubic root of 1221161309 is about 1068.8686644844.

The spelling of 1221161309 in words is "one billion, two hundred twenty-one million, one hundred sixty-one thousand, three hundred nine".