21102100992809 has 2 divisors, whose sum is σ = 21102100992810. Its totient is φ = 21102100992808.

The previous prime is 21102100992743. The next prime is 21102100992811. The reversal of 21102100992809 is 90829900120112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17217752727184 + 3884348265625 = 4149428^2 + 1970875^2 .

It is a cyclic number.

It is not a de Polignac number, because 21102100992809 - 2³⁶ = 21033381516073 is a prime.

Together with 21102100992811, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21102100992809.

It is not a weakly prime, because it can be changed into another prime (21102100992109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551050496404 + 10551050496405.

It is an arithmetic number, because the mean of its divisors is an integer number (10551050496405).

Almost surely, 2^{21102100992809} is an apocalyptic number.

It is an amenable number.

21102100992809 is a deficient number, since it is larger than the sum of its proper divisors (1).

21102100992809 is an equidigital number, since it uses as much as digits as its factorization.

21102100992809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46656, while the sum is 44.

The spelling of 21102100992809 in words is "twenty-one trillion, one hundred two billion, one hundred million, nine hundred ninety-two thousand, eight hundred nine".