1211209999921 has 2 divisors, whose sum is σ = 1211209999922. Its totient is φ = 1211209999920.

The previous prime is 1211209999913. The next prime is 1211210000069. The reversal of 1211209999921 is 1299999021121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 696782520225 + 514427479696 = 834735^2 + 717236^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211209999921 - 2³ = 1211209999913 is a prime.

It is not a weakly prime, because it can be changed into another prime (1211209999721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 605604999960 + 605604999961.

It is an arithmetic number, because the mean of its divisors is an integer number (605604999961).

Almost surely, 2^{1211209999921} is an apocalyptic number.

It is an amenable number.

1211209999921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1211209999921 is an equidigital number, since it uses as much as digits as its factorization.

1211209999921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 472392, while the sum is 55.

The spelling of 1211209999921 in words is "one trillion, two hundred eleven billion, two hundred nine million, nine hundred ninety-nine thousand, nine hundred twenty-one".