21111121109909 has 2 divisors, whose sum is σ = 21111121109910. Its totient is φ = 21111121109908.

The previous prime is 21111121109899. The next prime is 21111121109917. The reversal of 21111121109909 is 90990112111112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18363410415025 + 2747710694884 = 4285255^2 + 1657622^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111121109909 - 2³⁶ = 21042401633173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111121109009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10555560554954 + 10555560554955.

It is an arithmetic number, because the mean of its divisors is an integer number (10555560554955).

Almost surely, 2^{21111121109909} is an apocalyptic number.

It is an amenable number.

21111121109909 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111121109909 is an equidigital number, since it uses as much as digits as its factorization.

21111121109909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2916, while the sum is 38.

The spelling of 21111121109909 in words is "twenty-one trillion, one hundred eleven billion, one hundred twenty-one million, one hundred nine thousand, nine hundred nine".