21108027817 has 2 divisors, whose sum is σ = 21108027818. Its totient is φ = 21108027816.

The previous prime is 21108027767. The next prime is 21108027847. The reversal of 21108027817 is 71872080112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20767403881 + 340623936 = 144109^2 + 18456^2 .

It is a cyclic number.

It is not a de Polignac number, because 21108027817 - 2¹⁵ = 21107995049 is a prime.

It is not a weakly prime, because it can be changed into another prime (21108027847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554013908 + 10554013909.

It is an arithmetic number, because the mean of its divisors is an integer number (10554013909).

Almost surely, 2^21108027817 is an apocalyptic number.

It is an amenable number.

21108027817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21108027817 is an equidigital number, since it uses as much as digits as its factorization.

21108027817 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12544, while the sum is 37.

The spelling of 21108027817 in words is "twenty-one billion, one hundred eight million, twenty-seven thousand, eight hundred seventeen".