21108936109 has 2 divisors, whose sum is σ = 21108936110. Its totient is φ = 21108936108.

The previous prime is 21108936077. The next prime is 21108936131. The reversal of 21108936109 is 90163980112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19031582025 + 2077354084 = 137955^2 + 45578^2 .

It is a cyclic number.

It is not a de Polignac number, because 21108936109 - 2⁵ = 21108936077 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21108936169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554468054 + 10554468055.

It is an arithmetic number, because the mean of its divisors is an integer number (10554468055).

Almost surely, 2^21108936109 is an apocalyptic number.

It is an amenable number.

21108936109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21108936109 is an equidigital number, since it uses as much as digits as its factorization.

21108936109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 40.

The spelling of 21108936109 in words is "twenty-one billion, one hundred eight million, nine hundred thirty-six thousand, one hundred nine".