1211938616809 has 2 divisors, whose sum is σ = 1211938616810. Its totient is φ = 1211938616808.

The previous prime is 1211938616747. The next prime is 1211938616831. The reversal of 1211938616809 is 9086168391121.

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., 1075777616809 + 136161000000 = 1037197^2 + 369000^2 .

It is an emirp because it is prime and its reverse (9086168391121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1211938616809 - 2³⁷ = 1074499663337 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1211938616809.

It is not a weakly prime, because it can be changed into another prime (1211938616879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 605969308404 + 605969308405.

It is an arithmetic number, because the mean of its divisors is an integer number (605969308405).

Almost surely, 2^{1211938616809} is an apocalyptic number.

It is an amenable number.

1211938616809 is a deficient number, since it is larger than the sum of its proper divisors (1).

1211938616809 is an equidigital number, since it uses as much as digits as its factorization.

1211938616809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1119744, while the sum is 55.

The spelling of 1211938616809 in words is "one trillion, two hundred eleven billion, nine hundred thirty-eight million, six hundred sixteen thousand, eight hundred nine".