1221210209 has 2 divisors, whose sum is σ = 1221210210. Its totient is φ = 1221210208.

The previous prime is 1221210173. The next prime is 1221210223. The reversal of 1221210209 is 9020121221.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 810256225 + 410953984 = 28465^2 + 20272^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221210209 - 2⁸ = 1221209953 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221210239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610605104 + 610605105.

It is an arithmetic number, because the mean of its divisors is an integer number (610605105).

Almost surely, 2^1221210209 is an apocalyptic number.

It is an amenable number.

1221210209 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221210209 is an equidigital number, since it uses as much as digits as its factorization.

1221210209 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 1221210209 is about 34945.8181904502. The cubic root of 1221210209 is about 1068.8829314994.

The spelling of 1221210209 in words is "one billion, two hundred twenty-one million, two hundred ten thousand, two hundred nine".