21706868509 has 2 divisors, whose sum is σ = 21706868510. Its totient is φ = 21706868508.

The previous prime is 21706868479. The next prime is 21706868531. The reversal of 21706868509 is 90586860712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21455804484 + 251064025 = 146478^2 + 15845^2 .

It is a cyclic number.

It is not a de Polignac number, because 21706868509 - 2⁹ = 21706867997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21706868569) 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, 10853434254 + 10853434255.

It is an arithmetic number, because the mean of its divisors is an integer number (10853434255).

Almost surely, 2^21706868509 is an apocalyptic number.

It is an amenable number.

21706868509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21706868509 is an equidigital number, since it uses as much as digits as its factorization.

21706868509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1451520, while the sum is 52.

The spelling of 21706868509 in words is "twenty-one billion, seven hundred six million, eight hundred sixty-eight thousand, five hundred nine".